Cyclical Metapopulation Mechanism Hypothesis:

Generationally varying birth cohort speci c hypothalamic hormone levelscreate physiological, cognitive, and behavioral di erences in cyclical animal

populations, including human populations

Text: Janne Miettinen | PDF-version | ResearchGate: project page

Work-in-progress | First draft: Oct 2018 | Last update: Apr 7, 2021

Abstract

Hormone levels modulate both physiological and behavioral traits in animals. Cyclical animal

populations are proposed to be driven by population-wide multi-year hormone cycles. This

hypothesis presents how the proposed hormone cycle defines the average birth cohort specific

levels of hypothalamic hormones, thus creating generations with differing hormone levels.

Observed animal cycles are from approximately 4 years (small rodents) to 35 years (moose), but

it is proposed here that many human populations experience a similar generational hormone

cycle with an approximate length of 80 years.

Evidence of cyclical hormone levels is presented mainly from the documented lemming and vole

cycles, which is then compared to the theoretical generational hormone cycle of human

populations. Proxy statistics from human populations are then used to establish the same

generationally varying birth cohort specific hormone levels as in the presented cyclical animal

populations.

Since the population cycles have a migration phase that creates new populations and thus

eventually new subspecies and species, it is proposed that the presumed biological mechanism

that creates the cycles is an innate neural evolutionary mechanism, that accelerates speciation

through generationally varying hormone levels. These cycles also increase gene flow between

populations through the migration phase, and the high population count phase can theoretically

increase the speed of natural selection. The population cycles are therefore viewed as a

combination of already recognized evolutionary mechanisms; a holistic evolutionary

metapopulation mechanism in itself.

In addition, the hypothesis also includes a historical and sociological framework based on the

Strauss-Howe generational theory, that details an 80 year long generational cycle in the US

population. This repeating generational cycle consists of four 20 year generations, with each

generation having their unique typical behavioral traits. These repeating four US generations are

compared to the generations in the cyclical animal populations in order to establish that the

same cyclical hormone levels found in the cyclical animal populations, that presumably create

the physiological and behavioral changes in different phases of the cycle, create the

physiological and behavioral traits in the cyclical US generations.

Table of Contents:

1 Hormones and cycles

1.1 Animal population cycles

1.2 Generational hormone theory

2 Generational history and hormone levels

2.1 The Strauss-Howe generational theory

2.2 Historical oxytocin levels

… 2.2.1 Oxytocin and parenting intensity

… 2.2.2 Oxytocin and breastfeeding rates

… 2.2.3 Oxytocin and maternal age

… 2.2.4 Oxytocin and divorce rates

… 2.2.5 Oxytocin and alcohol consumption

… 2.2.6 A model of generational oxytocin levels

2.3 Historical dopamine and vasopressin levels

… 2.3.1 Dopamine levels

… 2.3.2 Group coherence and territoriality

2.4 Generational social hormone levels

… 2.4.1 A model of generational social hormone levels

… 2.4.2 Social hormones and political ideology

2.5 Other hypothalamic hormone levels

… 2.5.1 Sex hormones

… 2.5.2 Growth and thyroid hormones

3 Societal trends and social hormones

3.1 Current societal trends

3.2 Social hormones and societal group behavior

3.3 Neural in-group vs. out-group separation

3.4 Social hormones and populist nationalism

4 Group division and conflict

4.1 Group division

4.2 Societal paths of tightening group coherence

4.3 In-group empathy and scapegoating of the out-group

5 Initial conclusions

5.1 Possible societal trajectories

5.2 A review of societal actions against populism

5.3 Physiological issues

5.4 Evolutionary implications / cyclical evolution

5.5 Unresolved questions

References

1 Hormones and cycles

1.1 Animal population cycles

Many animal species have population cycles that are very repetitive. For example, the length of

population cycles are about 4 years for small mammals like lemmings and voles, 9 years for

larch budmoth, 10 years for snowshoe hare and forest Lepidoptera, and 35 years for moose.

(Myers, 2018 )(Wang et al., 2009 )(Krebs, 2010 )(Krebs et al., 2014 ) The small mammal cycles

are the shortest cycles in length.

There are over 1000 years of records of larch budmoth cycles that demonstrate the consistency

of these cycles – the average length being 9.3 years. (Esper et al., 2006 ) Below is a statistic from

the last century as an example of how highly regular the cycles can be in both length and

amplitude, with the statistic showing high consistency across over three decades.

Values 0.001-1000 indicate larch budmoth population density. (S)

Cyclical populations are very common in nature according to this study: “…we analyzed nearly

700 long (25+ years) time series of animal field populations, looking for large-scale patterns in cycles.

Nearly 30% of the time series were cyclic.” … “The incidence of cycles varied among taxonomic classes,

being most common in fish and mammal populations. Fully 70% of the fish and mammal species

comprised at least one cyclic population…” (Kendall et al., 1998/2002 ) It should be noted that

animal population cycles can break and stay dormant, but also recover, like the lemming

population cycle example statistic below illustrates.

Values 0-5 indicate lemming population density. (Ehrich et al.,2019 )

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Predators, limited food supply, and diseases have been suggested to drive the animal cycles, but

because the cycles do manifest even when these factors are excluded, it is likely that something

else is creating and controlling the length of these cycles: “…lemmings on islands are known to be

without predators and yet still undergo a 4 year population cycle.” (S, p. 79) “Numerous experiments

have been done in attempts to delay the decline or stop the population cycles of lemmings and voles by

feeding or excluding predators. These have had mixed results and Krebs concluded that predators can

‘modify’ population cycles, but that predator removal cannot stop cyclic dynamics. Similarly, food

addition experiments can modify vole densities but not drive cycles.” … “Overall, experimentally

stopping or starting population cycles has proven to be largely impossible.” (Myers, 2018 )

Increasing stress levels through increasing population density has also been used as a theory to

explain the cycles, but this idea too has been disproven: “In 1967, Dennis Chitty proposed that

larger and more aggressive voles would be selected for in increasing and high densities, and smaller

voles with delayed reproductive maturity in low densities. The ‘Chitty Hypothesis’ predicted that

variable selection would lead to a genetic shift over the 3 to 4 year cycle of voles. However, the genetic

shifts predicted by this hypothesis have not been observed and the levels of heritability of traits

required for the shift were unrealistically high.”

The end result is that after nearly a century of research into the animal population cycles, not

even one hypothesis exists that explains even one species’ cycles, while taking into account the

findings made by Krebs and others about the environmental factors not starting or stopping the

cycles. But if the environmental factors cannot explain the cycles, what could explain them?

This hypothesis suggests that the real explanation for the cycles lies within the endocrine

system that controls animal hormone levels and therefore modulates both their behavior and

biological traits. It is important to note that the term ‘ hormone levels‘ used throughout this text

means that the hypothalamic neurons that secrete hormones are either small and inefficient or

large and more efficient, like is presented in the lemming and vole studies below. In addition,

the term ‘hormone’ will be used throughout the text, even though some of these same molecules

also work as neurotransmitters in the brain, where the levels of these neurotransmitters directly

modulate behavior. (S)

Two Russian neurobiological studies have focused on the generational changes to the endocrine

system in voles and lemmings during their four year population cycles, and these studies state

that there are large variances between generational hormone levels, including dopamine,

oxytocin, vasopressin, and other hormones secreted by the hypothalamus. (Arshavskaya et al.,

1989 /PDF)(Vladimirova et al., 2006 ) This is due to generational changes/differences in the

parts of the hypothalamus that produce and secrete hormones. These two studies will be used as

a template for the suggested human generational hormone cycle. Other studies regarding

cyclical populations have largely made similar findings using external measurements such as

larger testicles during the increase phase and higher ACTH/cortisol levels during the decline

phase. (Sheriff et al., 2011 )

Below are key excerpts from these two mentioned studies as examples displaying the hormonal

nature of the four year cycle: the 1989 lemming study measured the changes to the mass of the

hypothalamic neurons and their effects on the endocrine system, and the 2006 vole study

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measured the percentage of efficient vs. inefficient hypothalamic neurons in detail – both

studies confirmed large generational variance in the different regions of the hypothalamus.

These studies will be referred to throughout this hypothesis in more detail, and will not yet be

explained in full detail at this point, but the two excerpts below largely represent the studies’

key findings regarding lemming and vole generational hormone levels.

Generational variance in the lemming endocrine system during different phases of the cycle,where the size of hypothalamic neurons secreting hormones/neurotransmitters affects the sizesof organs that secrete hormones. Phases II and III roughly represent the changes during thecycle’s last year/quarter. (Arshavskaya et al., 1989 /PDF)8

The number of neurosecretory cells with high amount of oxytocinor vasopressin in different parts of the voles’ hypothalamus at

different phases of the four year cycle. (Vladimirova et al., 2006 )OX = oxytocin, VP = vasopressin, PVN = paraventricular nucleus,SON = supraoptic nucleus. The phases of the population cycle arenamed; the ‘Depression’ phase represents the ending and thebeginning of the cycle (4th/1st phases)

Because cyclical animal populations see hormone levels fluctuate throughout the cycle, this

means that a population’s physiological and behavioral traits are also fluctuating. This also

means that the location in the cycle where an individual is born determines the probability of

this individual having a certain configuration of hormone levels and the physiological and

behavioral traits that these hormone levels promote. The endocrine system uses hormone levels

to control and coordinate for instance stress response, reproductive behavior, mood, and

development.

In spite of there being many attempts during the past century to explain the animal population

cycles through various environmental factors, basically all explanations and theoretical models

have been quite severely lacking in evidence and/or repeatability, resulting in a situation that no

species’ cycles are truly understood. But a biological mechanism that controls the generational

hormone levels would explain the populations cycle in a way that is not dependent on

environmental factors like predators or food supply.

And there is one mammal species that is proposed to be cyclical, and that is humans. Humans

are mammals, and mammal populations are among the more frequently cyclic animal

populations. (Kendall et al., 2002 ) And there exists a sociological cycle theory that describes an

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80 year generational cycle going on for centuries in the US, which includes four phases and four

generations, just like with the lemming and vole cycles. The Strauss-Howe generational theory

describes in detail how these cyclical four generations have distinct behavioral traits, that repeat

in a four phase cycle in the same order every time.

This hypothesis presents a generational hormone theory, which aims to provide evidence that

most Western human populations experience the same generational changes to their

hormone/endocrine system like the cyclical animal populations do. The suggested cycle length is

roughly 80 years for human populations. This implies that the human generations also have

different physiological and behavioral traits, since each generation presumably has unique

average hormone levels. The documented findings made in the mentioned lemming and vole

studies will be used throughout this hypothesis to demonstrate that humans have a very similar

generational hormone cycle, and that this cycle is in sync with the Strauss-Howe generational

theory’s observations about generational behavioral traits and also historical societal change.

The presented generational hormone theory concentrates on the Western nations, since the

Strauss-Howe generational theory covers mainly the US generations, but because those

generations share many cultural and behavioral similarities with concurring generations in

other Western nations, this leads to suspect that the Western generations have more in common

than just cultural similarities; presumably common generational hormone levels. Nearby

cyclical animal populations are often in sync regarding the phases of the cycles. (Krebs et al.,

2017 )(Tähkä et al., Endocrine aspects of population regulation in the genus Clethrionymus , Mem.

Soc. fauna Flora Fenn., 1984) This hypothesis also presents that Russia is possibly undergoing the

same generational cycle, but lags about 15-20 years behind the US, and that many Eastern

European countries are some where in between, lagging roughly 10 years the presumed US cycle.

In addition, almost all of the cyclical animal populations are located between northern latitudes

30 and 70, and those latitudes also include all the Western nations on the Northern Hemisphere

and Russia.

1.2 Generational hormone theory

To shortly characterize the premises of the generational hormone theory: it is proposed that

most Western nations have generationally varying/oscillating hormone levels that shape the

typical behavioral and also physiological traits of generations. These are the very same

generational traits that the Strauss-Howe generational theory presents from the Anglo-Saxon

generational history. These varying hormone levels also affect group coherence and the “in-

group vs. out-group” setting, that has already been established through a multitude of studies in

both social psychology and neurology, and these changes to group coherence follow the Strauss-

Howe generational theory’s 80 year cycle of low/high group coherence. (Lewis et al., 2010 )

(Lewis & Bates, 2017 )(S)(S) (Dopamine levels have a major effect on the tightness of larger

social groups like nations, and dopamine levels are presumed to be in sync with the generational

vasopressin levels that are presented in chapter 2.)

The graph below presents the presumed average birth cohort hormone levels found in Western

nations. It is important to note that the graph below represents presumed birth cohort levels of

hormones, while some other graphs present presumed societal effects of hormones, which

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manifest roughly 30 years later after a birth cohort has been born, as is explained later in more

detail. (An example would be that, according to the graph below, the highest point in sex

hormone levels in young adults in the Western societies during the 21st century was presumably

close to the year 1970, and the following lowest point was close to the year 2010.)

Theoretical average birth cohort specific hormone levels in Western nations, backed up bystatistics that are presented in chapter 2. ‘Sex hormones’ represent presumedgonadotropin-releasing hormone levels.The ‘growth hormone’ curve represents thepresumed levels of the growth-hormone-releasing hormone that is secreted by thehypothalamus.

The generation hormone theory aims at providing a biological basis for the Strauss-Howe

generational theory and uses it as a framework along with historical proxy statistics and the

animal population cycle studies to establish a generational hormone cycle for human

populations. Especially oxytocin, dopamine, and vasopressin are at the center of this theory,

since those are hypothalamic social hormones that modulate group behavior in general: oxytocin

is relevant in the context of family and friends, dopamine is relevant to large-scale group

coherence, and vasopressin is relevant in the context of territoriality and group aggression. It is

important to note that there obviously are other hormones that affect social group behavior, but

since they are not secreted from the hypothalamus, they are not taken into account in this

hypothesis.

The generational hormone theory aims at binding these hormone’s behavioral effects into

societal phenomena, especially large-scale in-group vs. out-group behavior, and after that

connect these established types of group behavior into historical eras in order to find correlating

points in history that are repeating regularly every 80 years. From the viewpoint of sociology,

the generational hormone theory takes both micro and macro levels into account by looking

separately at individual and group behavior, both of which are modulated by hormone levels.

It should be noted that terms like nationalism and globalism are only social constructions that

are always tied to their historical context. Nationalism and globalism could be replaced with

terms of tribalism vs. cosmopolitanism or some other way to convey the idea of a society’s social

coherence and a society being more open/closed to outside groups. The effects of social

hormones on ideology cannot therefore be bound too much to any terms of language because

the roots of ideological tendencies are situated in biology as is presented in later chapters: the

societal effects of low/high hormone levels manifest in different ways depending on the social

structure of the selected point in history, be it a feudal kingdom in 12th century England, a

Germanic tribe in 15th century, or a nation belonging to the EU in the 2020s. This is why mainly

the terms nationalism and globalism will be used to in order to illustrate differences between

eras of low and high group coherence.

The historical observations made throughout the generational hormone hypothesis are made

only to create a link between 1) presumed changes in generational hormone levels in human

populations that are similar to the animal population cycles and 2) the Strauss-Howe

generational theory, but not to suggest that hormone levels in some way have created historical

events.

To better explain the presumed generational cycle, an example of varying hormone levels

through a period in time is the menstrual cycle: women in their reproductive years tend to have

mood swings that are caused by changing hormone levels during their menstrual cycle, and the

women react according to their mood, like with increased anxiety, depending on the phase of

the cycle. But the menstrual cycle also has an effect on memory and spatial skills for instance,

demonstrating that varying hormone levels impact both behavior and cognitive skills (and even

the structure of the brain). (Pletzer et al. 2019 )(S)

Women’s cognitive skills change during the menstrual cycle due to fluctuating hormone levels. (S)

Even though menstrual synchrony among women is still a debated subject ( S), if the synchrony

was occurring, it would mean that there would be also behavioral and physiological trait

synchrony among those women during different phases of the month. This is essentially the

same thing that this the generational hormone theory is suggesting to be happening in an 80

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year cycle with generations: birth cohort specific average hormone levels affect each

generations’ average behavioral and physiological traits, and these traits are presumably listed

by the Strauss-Howe generational theory. And just like the menstrual cycle, that is a ‘multi-

oscillatory circadian system’, the generational hormone cycle is presumed to have different

phases with different hormone level configuration. (Simonneaux & Bahougne, 2015 )

And very similarly to the animal population cycles not being sufficiently explained by any

traditional methods that look only at environmental factors, not a single species’ menstrual

cycle length variations have been successfully explained by using environmental factors:

“Although cyclical temperature changes are experienced by many species, as are fluctuations in food

supply, rainfall, and salinity, their precise effects and those of many other stimuli, independently or in

combination, have not yet been defined for any species.” This leads to suspect that menstrual cycles

are presumably also controlled by something else than environmental factors. (More on this

speculation in chapter 5.5.)

In effort to keep this hypothesis as short as possible, genetic factors of individuals are confined

out of this hypothesis, since on a level of a population the genetic differences between

individuals and generations are evened out. Hormone receptor SNPs are negated at this point for

the same reason. There are differences in the mean genetic and SNP distribution between

nations and continents, but for the moment, this fact is left aside.

Transgenerational epigenetic effects are left aside for now, because they are more case

sensitive, but could theoretically contribute to the generational traits in some ways, since stress

receptivity of generations presumably changes during the cycle. And since hormones act as

epigenetic signals in development, as is presented in chapter 2.1, epigenetics are taken into

account, but not in a transgenerational way at least for now. (In 2019 this hypothesis included a

theoretical framework on how the fluctuations in hormone levels might be due to epigenetic

effects between generations, but this framework was abandoned due to several reasons, one of

them being that it would be highly unrealistic for such a epigenetic cycle – for all hypothalamic

hormones – to manifest as coherently as what the cycles have been documented to be between

different species and also different environments.)

Differences in hormone effects between sexes are currently mostly negated, but will be

implemented later on. Biologically the proposed human generational hormone cycle is very

similar to the documented lemming and vole generational hormone cycles. Because functions of

the hypothalamus have been tightly conserved through the mammalian evolution, this makes

findings from rodents largely translatable to humans. (Caldwell & Albers, 2015 )(S)

Hypothalamic hormones have a multitude of physiological and behavioral effects in different

species, but only those hormone effects are accounted for that have 1) behavioral effects relevant

to this hypothesis and 2) physiological functions that are used to find historical hormone levels

by using proxy statistics (like breastfeeding statistics for oxytocin).

– After the introductory chapter 1, chapter 2.1 presents the Strauss-Howe generational cycle in

more detail; 2.2.1 reviews how time spent with children is linked to the parent’s oxytocin levels;

2.2.2 reviews historical evidence of breastfeeding initiation and its connection to oxytocin; 2.2.3

reviews the average maternal/paternal age and its connection to oxytocin; 2.2.4 reviews

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historical divorce rates and their connection to oxytocin levels; 2.2.5 ties generational oxytocin

levels to changing alcohol consumption rates in history; 2.2.6 presents the generational

oxytocin levels based on the previously presented proxy statistics; 2.3.1 review proxy statistics

to find generational dopamine levels; 2.3.2 ties eras of high/low group coherence to fluctuating

dopamine levels and includes vasopressin into eras of high/low territoriality, and explains how

individual feelings are represented on a larger social scale as values in institutions, and also

explains how dopamine has been used in hypotheses of human social evolution before; 2.4.1

presents a model of the generational hormone cycle with oxytocin, dopamine, and vasopressin

included in it, and explains their effects on the social mood; 2.4.2 explains how generational

social hormone levels presumably modulate generational voting behavior; 2.5.1 links lower

levels of sex hormones to the reproductive difficulties experienced during the early 21st century

and also other health issues; 2.5.2 reviews growth and thyroid hormones.

– Chapter 3.1 that lays out the current societal trends of populist nationalism and challenged the

old insufficient explanatory models used to describe their root causes, 3.2 is a short introduction

to how hormone levels are related to history; 3.3 is an introduction to oxytocin, dopamine, and

vasopressin and their effects on individual and group behavior; 3.4 looks at how social hormone

related traits are linked to the appeal of populist nationalism.

– Chapter 4.1 takes a closer look at chimpanzees exhibiting similar group division patterns as

humans do; 4.2 lays out possible paths small and large groups undergo when group coherence

tightens; 4.3 ties the biological roots of scapegoating to increasing in-group empathy.

– Chapter 5.1 presents initial conclusions based on the findings made throughout this

hypothesis; 5.2 lists commonly suggested ideas on how to suppress populism; 5.3 previews the

trajectories of issues related to physiology; 5.4 presents the evolutionary implications of the

theoretical oscillating generational hormone cycle, including the formation of new subspecies

and species through the migration phase; 5.5 includes some currently open questions.

This hypothesis has been a personal project and a byproduct of research done while writing a

master’s thesis looking at oxytocin and vasopressin levels being connected to empathy and

aggression, while simultaneously reading about the Strauss-Howe generational theory, and

then evaluating if generational hormone levels could explain the generational behavioral traits

that the Strauss-Howe generational theory details. (McLean et al., 2017 )(S) This hypothesis

has therefore been growing organically without any other specific aims than to find out if there

really could be a generational hormone cycle in human (and other animal) populations.

Sources used are mainly from the fields of neurobiology, neuropsychology, chronobiology, and

sociology; the combination of these can be described as sociochronobiology. (S) Quotes are used

to underscore some of the most important aspects of the biological and historical evidence

central to this hypothesis. Sources are linked almost always only once in their most relevant

context, and at times are a collection page that may not be a strictly scientific source. Although

much more could be stated about many aspects regarding this hypothesis, the text is

streamlined in its current state to be as coherent and easily accessible as possible.

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2 Generational history and hormone levels

2.1 The Strauss-Howe generational theory

During the 1980s, historians William Strauss and Neil Howe started to write a book about the

history of the US generations labeled Generations. (1991 C-SPAN interview) In 1997 they

released The Fourth Turning book, that went even further in describing the dynamics of their

theoretical generational cycle. (1997 C-SPAN interview) According to the interviews of these

generational historians, before this they had come across the repeating generational cycle

(presented in this chapter) independently in their studies, and only after this meeting each other

and combining their research towards a common goal of presenting the history of US

generations.

The Strauss-Howe generational theory details a four generation cycle that goes on roughly at

intervals of 2030-2010 | 2010-1990 | 1990-1970 | 1970-1950, etc., with each of the four

generation having detectable individual and group behavioral traits. (S) The years are

approximations and vary slightly between the books and this theory, since the books are based

on historical observations while this theory is based on a more coherent biological cycle. (S)

The cyclical four 20 year generations are introduced next, and then it is explained how they form

a repeating cycle of 80 years in total like William Strauss & Neil Howe have documented in their

books including Generations (1991) and The Fourth Turning (1997). (S) One full 80 year cycle is

called an Anglo-American saeculum, and the repeating four generations span all the way back to

the 15th century England. Since this chapter includes a lot of historical claims, the sources and

quotes are not presented to be indisputable facts, but are used to construct a “bridge” between

the Strauss-Howe generational theory and the presumed generational hormone levels in many

Western nation that are presented in this chapter, which seem to be very similar to the

fluctuating population-wide hormone levels in different phases of cyclical animal populations.

Strauss & Howe use the word ‘turning’ to describe a roughly 20-year long phase. A 1st

generation is born during a 1st turning, and that generation is the Boomers in the current

generational cycle. The generations and their traits were easily observable during the 20th

century (Baby Boomers, Generation-X, Millennials) in most Western nations, especially in the

U.S., due to the increasing societal freedoms and consumerism of the past century. Changes to

youth culture mostly generated in the U.S. and spread on from there to other Western nations

that were receptive to these movements, presumably by them having similar cyclical hormone

levels (as is presented later on), which would be similar to the cyclical animal populations that

have their cycles in sync with other nearby cyclical populations.

The most volatile point in the 80 year Strauss & Howe generational cycle has historically been

the last (4th) turning, when a 1st generation, the so called Prophet/revolutionary generation

(Baby Boomers in the current cycle), is largely holding the places of maximum civic and

economic power. This has historically been a time of societal turmoil: old beliefs are challenged,

group coherence tightens, institutions are reshaped to serve the new goals, and the status quo is

changing rapidly towards the end of a 4th turning. (More on how institutions evolve through

increasing group coherence in chapter 2.3.2.)

Strauss & Howe are not the only ones to have noticed such a generational pattern in history, as

sociologist and historian Jack Goldstone has also observed a generational pattern manifesting

throughout human history: “Goldstone was also encouraged by the publication in 1978 of Colin

McEvedy and Richard Jones’s Atlas of World Population History, in which they highlighted an

“astonishing synchronicity” in population booms and busts across Eurasia over millennia. A few

months into his number-crunching, he had his eureka moment: “It was astounding: there really was a

three-generation surge in population growth before every major revolution or rebellion in history.””

(S)

Other historians that Strauss & Howe have listed in The Fourth Turning, including Arnold

Toynbee and Quincy Wrigth, also have located similar cyclical generational patterns in many

historical cultures. Strauss & Howe note that even the renowned political philosopher Polybius

found a very similar generational cycle in second century B.C. when he studied the histories of

Greco-Roman city-states.

Below are short descriptions of the four turnings accompanied by short quotes from the book

The Fourth Turning (and approximate years of birth from the current cycle).

1st turning (1943-1960): “An upbeat era of strengthening institutions and weakening individualism,

when a new civic order implants and the old values regime decays.” The society is unified and there

is optimism about the future, institutions are trusted. The society eventually starts a movement

towards globalism and liberalism, but nationalistic/patriotic pride is still strong. A 1st

generation is born into an era of cooperation, and is a more optimistic, daring and selfish

generation than the previous (4th) generation. This sense of optimism has been observed even

in the offspring of holocaust survivors. (S) A 1st generation is historically the populist

generation once they gain major political power during a 4th turning.

2nd turning (1961-1981): “A passionate era of spiritual upheaval, when the civic order comes under

attack from a new values regime.” In a second turning the 1st generation leads the youth

revolution and the more rigid nationalistic culture of the first turning makes way for a strong

culture of liberalism, much through 1st generation young adults. A 2nd generation is born and

raised very loosely, becoming a generation of independent individuals, driving the rise of

individualism in their young adulthood during the next (3rd) turning.

3rd turning (1982-2004): “A downcast era of strengthening individualism and weakening

institutions, when the old civic order decays and the new values regime implants.” In the 3rd turning

the family structures are weak, individualism is strong, and anti-social behavior like crime is

common. A 3rd generation is born into a relatively peaceful liberal world, and they become more

cosmopolitan in their ideological views than the previous generations. General trust towards

institutions starts to decay, and this accelerates during the next (4th) turning.

4th turning (2005-2027): “A decisive era of secular upheaval, when the values regime propels the

replacement of the old civic order with a new one.” In a 4th turning the 1st generation enters

positions of most political power and nationalistic coherence (or divide) tends to reach its peak

towards the end of the turning (different paths are assessed in chapter 4). (S) The 1st generation

with their confidence and capital power tend to drive the economic bubbles to new heights

before a bust, like in 1929 and 2007. (S) Group tightness and coherence increases, ideological

sides are being chosen at an accelerating pace, and cooperation among (possible) opposing

factions of society deteriorates. This crisis era will basically either unify or divide a society even

further. Information outlets and individuals with large audiences like celebrities begin to weigh

in their opinions more and more in the increasingly polarized public ideological debate. A 4th

generation is born, they are sensitive, sentimental, and their stress receptivity is high, just like

today’s youth is often referred to as “snowflakes” by the older (and also bolder) generations.

“The social mood changes” Strauss & Howe often remind their readers of what happens in a 4th

turning once the so called crisis era begins.

The Strauss-Howe generational theory states that if a society has issues within, these problems

will grow larger once the anxieties of a 4th turning begin, and this is presumably due to

increasing vasopressin levels, which correlate with higher anxiety levels, since vasopressin is

anxiogenic. (Neumann & Landgraf, 2012 ) High vasopressin and dopamine levels therefore

result in anxious and polarizing group behavior, which is exactly what the Western nations

experienced during the 2010s (just like the Strauss-Howe generational theory predicted in the

1990s). This movement can be observed for example in the US statistic below that illustrates the

party divide beginning to increase even though the issues have not become more polarized.

The political party affiliation in the US has grown since the late 00s,even as the stances on issues have not become as divided, but remainedmuch steadier. (S)

In other words, the stance on political issues has not changed much on average in over 20 years,

but the group affiliation to political parties has become much stronger. Since a party is an

ideological in-group, this statistics essentially tells how the in-group identification has gotten

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stronger. The partisan divide began between 2004 and 2011, and a similar trend can be observed

to have happened in the UK in the beginning of the 2010s.

Polarization in the UK (by birth cohort) begun in the early 2010s. (S)

There obviously are differences in individual hormone levels and behavior, but looking at a

generation as a whole averages out these individual differences and, for example, youth culture

and voting behavior are good indicators of how a generation acts and what are their preferences

and behavioral traits. As most people are married to and have a majority of their friends from

their own generation, this enhances the effects of hormone levels to individual and group

behavior through behavioral synchrony. (Sources to be added…)

To very shortly further characterize the generations by echoing the Strauss-Howe generational

theory, listed below are youth culture examples from the current cycle, highlighting the

generational social mood found in music and movies for the 1st (revolutionary/optimistic), 2nd

(individualistic/darker), 3rd (communal/heroic) and 4th (sentimental/caring) generations.

Aesthetic experiences like music activates the brain’s reward system (Sachs et al., 2016 ), and

the four generations have different preferences in what kind of music they prefer to listen to.

Since aesthetic experience is basically a biological mechanism reacting to sensory input, this

implies that different generations have different brain structures that affects their behavior, and

different hormone levels can change the brain structure due to brain plasticity. (Rajamani et al.,

2018 )(S)

1st: Boomers | Music: The Beatles, The Rolling Stones, Elvis. | Movies: Rebel Without a Cause,

Easy Rider.

2nd: Generation X | Music: Nirvana, Metallica, Madonna. | Movies: Star Wars and Halloween

franchises.

3rd: Millennials | Music: Foo Fighters, Spice Girls, Lady Gaga. | Movies: Harry Potter and Marvel

franchises.

4th: Generation Z | Music: Ed Sheeran, Shawn Mendes, Billie Eilish. | Movies: The Hunger

Games and The Maze Runner franchises. (More cultural examples, especially from and beyond

the 20th century, can be found in books by Strauss & Howe, which address the typical cultural

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interests of the four generations.)

Since hormones act as epigenetic signals in development, the presumed hormone cycle could

presumably modulate the average phenotypes of entire generations, resulting in synchronized

average generational behavioral and physiological traits. (Fowden & Forhead, 2009 ) This

would result in generations to have their unique generational behavioral phenotypes when

comparing different generations inside one full cycle. (Crawley, 2008 )(S) (The term

‘behavioral phenotypes’ has sometimes been used to describe mental illnesses, but here it is

used to describe the presumed average behavioral traits of generations.)

To back up the claim that the four different generations have different hormone levels, this

chapter 2 presents evidence of generational oxytocin, dopamine, vasopressin, sex, growth, and

thyroid hormone levels, and inserts them to the theoretical generational hormone level chart.

Chapter 2.2 presents historical proxy statistics of child nurture intensity, breastfeeding,

maternal/paternal age, divorce, and alcohol consumption rates in order to establish common

points in history when oxytocin levels have been high or low. Chapter 2.3 looks at dopamine and

vasopressin levels using other proxy statistics. These findings are bound together in chapter 2.4,

where it is presented that different generations have different levels of social hormones (on

average), and how these varying levels of social hormones affect the generational behavioral

traits and the social mood during the different turnings as is described in the Strauss-Howe

generational theory.

Although only proxy statistics are available for dopamine, vasopressin, and oxytocin levels

regarding human populations, the proxy statistics may actually be a much more accurate way of

measuring birth cohort specific hormone levels than direct measurements from blood samples.

This is because the mentioned hormones are secreted when needed (compared to hormones like

testosterone, which have more of a timed and longitudinal secretion rate), but if the

hypothalamic neurons are small and ineffective, the effects do not manifest like they would if

the hypothalamic neurons were large and effective. This is why proxy statistics give “real world

results” in comparison to laboratory measurements.

For example, oxytocin is released when a baby sucks on the mothers nipple, and if not enough of

oxytocin is released, there will not be milk ejection. The situation will also result in less of a

bond between the child and a mother, meaning that the mother’s nurture will likely be less

intensive as the child grows. So what is good about the proxy statistics is that they are tied to

both the amounts of hormones secreted and the situation at hand, not to a single measurement

in a lab like how hormone levels are conventionally measured.

2.2 Historical oxytocin levels

2.2.1 Oxytocin and parenting intensity

Higher oxytocin levels in parents leads to more time spent with children. ( Gordon et al., 2010 )

The Strauss-Howe generational theory states the following about child nurture (S) intensity: 1st

turning nurture is relaxing, 2nd turning nurture is underprotective, 3rd turning nurture is

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tightening, and 4th turning nurture is overprotective, after which the next 1st turning child

nurture is once again loosening. The graphic below, that is taken from the book Generations

(1991), illustrates the 80 year cycle in nurture intensity (where the 2nd turning is roughly from

1965 to 1985 in the current cycle).

‘Turnings’ and ‘generations’ (red text) have been later added for clarity. Social ‘eras’ are explainedin detail in Strauss & Howe’s books Generations (1991) and The Fourth Turning (1997).

According to the statistic below, it seems that the 1970s were the time when American parents

spent the least time with their children. The statistic shows a pattern similar to the

breastfeeding initiation and maternal/paternal age statistics that are reviewed next. The bottom

year is close to 1975 and the top year seems to be close to 2005-2010, repeating the same years

as with the breastfeeding rate and paternal age statistics. There is also a steeper climb from 1975

to 1985 like with the breastfeeding rate and maternal/paternal age statistics (reviewed next).

Weekly hours spent with children under age 5, the low peak being in the 1970s, and the high peakbeing in the 2000s. (S)

being in the 2000s. (S)

The statistic highly correlates with the Strauss-Howe generational theory regarding nurture

intensity. In the 1970s bringing up children was much more carefree than in the 2000s. (S) Other

Western nations also show large increases in parenting time since the 1970s. (Sani & Treas, 2016

)

2.2.2 Oxytocin and breastfeeding rates

Breastfeeding initiation statistics should correlate with oxytocin levels, as breastfeeding

requires oxytocin to enable the milk let-down reflex. (Augustine et al., 2017 )(S)(S) “Circulating

oxytocin is critical for normal birth and lactation. Oxytocin is synthesized by hypothalamic supraoptic

and paraventricular neurons and is released from the posterior pituitary gland into the circulation…

While it might be controversial as to whether oxytocin plays an indispensable role in parturition, the

critical role that oxytocin plays in milk let-down during lactation is not disputed. The release of milk is

mediated by secretion of oxytocin from the posterior pituitary gland, and oxytocin’s action at OTR

[oxytocin receptor] in the mammary gland induces a rise in intra-mammary pressure and release of

milk: an oxytocin-mediated reflex upon suckling.” (Scott & Brown, 2013 )

All available breastfeeding statistics from Western countries indicate that there is a low point in

breastfeeding rates close to 1965-1975: U.S. (Ryan, 1997 ), Australia (S), Norway (S), Sweden

(S), New Zealand, and England & Wales. Even Japan shows a similar curve. ( Inoue et al., 2012 )

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A verbal statement about the US rates reinforces the statistics that the rates were higher in the

1930s than in the 1970s: “Seventy-seven percent of the infants born between 1936 and 1940 were

breastfed; the incidence declined during the subsequent decades to about 25% by 1970.” (Institute of

Medicine, 1991 )

When looking at earlier centuries for similar patterns of low points in breastfeeding in the US,

there unfortunately are no breastfeeding statistics from the 19th century, but here is a quote

from the year 1887 that provides answers: “Then, bizarrely, American women ran out of milk.

“Every physician is becoming convinced that the number of mothers able to nurse their own children is

decreasing.” Another reported that there was “something wrong with the mammary glands of the

mothers in this country.”…In the United States, nineteenth- and early-twentieth-century physicians,

far from pressing formula on their patients, told women that they ought to breast-feed. Many women,

however, refused. They insisted that they lacked for milk, mammals no more.” (S) The inability to

breastfeed is a probable indicator of low oxytocin levels, and like the Strauss-Howe generational

theory states, nurture intensity was also low during this period.

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And from 80 years earlier, this text may provide answers: “As with so many popular trends, there

came a backlash against the use of wet nurses. Come the late 1700s/early 1800s—as part of the reform

movements that swept across the social landscape of Europe and the United States—many women and

men were calling for a return to in-home breastfeeding of babies by their own mothers.” (S) If there

were calls to return to breastfeeding, that could indicate that the breastfeeding rates by

biological mothers quite possibly have been low during that point in history. (And as a side note,

the quote also mentions the social reform movements happening at the same time, just like

during the 1960s and 70s, decades of large social reforms in Western nations.)

Historical UK breastfeeding rates closely echo the findings from the U.S. The following quote

enforces this presumption: “The interwar [between WW1 and WW2] years saw the start of a long,

steady decline in breastfeeding… breastfeeding rates in mothers leaving the postnatal wards dropped

to below 20 per cent around 1970… there is no doubt that the 1970s represent a nadir in breastfeeding

rates… But, for whatever reason, it is a fact that breastfeeding rates were much lower in the 1970s than

in the decades before, and lower than they are now [2007].” (S)

In addition, since oxytocin is also required for parturition, and there is a negative correlation

between caesarean section and breastfeeding rates, this enforces the presumption that

breastfeeding statistics would correlate with the mother’s oxytocin levels. (Blanks & Thornton,

2003 )(Hobbs et al. 2016 )(Smith, 2007 )

As for the connection between child the child nurture intensity, Generation X, a 2nd generation,

was born during 1965-1983 (estimations slightly differ between Western nations and but also

between generational historians) and would, according to the Strauss-Howe generational

theory, be a 2nd generation that received underprotective nurture. (S) Parent’s high oxytocin

rates lead to more affectionate/intense nurture, and low oxytocin rates lead to less

affectionate/intense nurture. (Gordon et al., 2010 ) The Australian breastfeeding, which are

probably more accurate than the US statistic (that are comprised of three different sources),

illustrates that rates are at the lowest point during the birth of Generation X, which correlates

with low nurture intensity, and this is presumably due to low oxytocin levels in the parents.

(Gordon et al., 2010 )(S)

The Strauss-Howe generational theory’s nurture intensity is lowest for the 2nd generation, and

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the Generation X in Australia was born in 1965-1983.

The statistical evidence therefore supports the presumption that the Strauss-Howe generational

theory’s 80 year nurturing intensity cycle is actually a generational oxytocin cycle with a span of

80 years. Maternal/paternal age, divorce rates and alcohol consumption rates reviewed next add

more support to this claim.

2.2.3 Oxytocin and maternal age

Higher oxytocin levels have been linked to higher maternal age. ( Erickson et al., 2019 ) Taking

the years 1970-75 as the presumed low point for oxytocin levels like with the breastfeeding

statistics, there seems to be a high degree of correlation: the UK (S), Canada (S), Australia (S),

Denmark (S), Austria (S), the US (S), the Netherlands (S), Norway (S), and France (S) all show

very similar statistics with low points occurring close to the year 1970. (In the US the lowest

point was actually closer to 1965, but the curve starts to go up close to 1970-75.) Japan is

showing a similar but less pronounced effect (S) with only a minor decrease in maternal age, but

the breastfeeding stats are also less varied in Japan when compared to other nations where stats

are available.

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The similarity between these statistics is very apparent, and they also share a high degree of

similarity with the breastfeeding charts. If these proxy statistics indeed do indicate oxytocin

levels, it would implicate that the average age of motherhood may be strongly modulated by

oxytocin levels.

What is possibly even more important to note is that the statistics display that physiological and

behavioral effects of oxytocin go hand in hand, indicating that hormone levels have a large

impact on the decision of at what age to have children, something that is normally considered to

be a very personal decision. Since parenting intensity is also linked to these same curves, it

enforces the idea that generational oxytocin levels modulate both behavior and physiological

effects at the same time.

Previous statistics have taken only mothers into account, but the statistic below of average

paternal age show yet again a very similar curve when compared to the maternal age and

breastfeeding statistics. (S) Men become fathers being a few years older than women on

average, which is why the stats lag a few years from the statistics of maternal age. (S) The graph

is very similar to the maternal ages presented before with the lowest point being during the

1970s, with only a few European countries lagging behind: Russia, Poland, Hungary, Estonia,

Czech Republic from the east and Spain from the south. (S)

Mean paternal age in European countries. (S)

Having children later in life is very similar to the lemming cycle, since they reproduce later (and

less) during the peak phase of their cycle (Erlinge et al., 2010 ), their peak being roughly

equivalent to a 4th turning. In human studies higher baseline levels of oxytocin has been

attributed to higher prevalence of infertility, which implicates that reproductive systems are

less efficient during high levels of oxytocin, that being again during the 4th turning. (Lui et al.,

2010 ) (Chapter 5.1 addresses issues related to sex hormone levels and fertility.)

As for other possible explanations why the maternal age has risen from the 1970s, a commonly

held belief by many in the field of sociology is that labor force participation percentage of

females would somehow affect the age when women have children. But looking at longitudinal

statistics from the US, Canada, and the UK, it is quite evident that these statistics have little in

common with the other statistics presented in this chapter. This implicates that the commonly

held belief of female labor force participation affecting maternal age is likely a false belief.

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Long-run perspective on female labor force participation rates, 1890 to 2016. (S)

2.2.4 Oxytocin and divorce rates

Divorce rates are presumed to be connected to oxytocin levels, as studies show that lower

oxytocin levels correlate with higher divorce rates. (S) Lower oxytocin levels lead to higher rates

of break-ups in non-married couples as well. (Sunahara et al, 2019 ) Therefore it is not a

surprise to see the start of the 1970s to witness a large increase in divorce rates in many Western

countries as the statistics below illustrate, because that is also approximately the low point in

the oxytocin levels as indicated by the breastfeeding initiation charts. Statistic from the U.S.

suggest that average oxytocin levels for married couples were at their lowest point at around the

1970s and then went higher again during the 1980s.

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Legislative restrictions held back the divorce rates in countries like Australia ( S) and New

Zealand (S), which explains the very clear spikes in divorce rates once those legislative

bottlenecks were removed. This is a good example how a demand for something through

low/high hormone levels can create demands for new legislation.

In addition to the divorce rates increasing, the percentages for marital quality dropped at the

same time: “…marital quality fell during the ’70s and early ’80s. In the early 1970s, 70% of married

men and 67% of married women reported being very happy in their marriages; by the early ’80s, these

figures had fallen to 63% for men and 62% for women.” (S) The Strauss-Howe generational theory

states that a 2nd generation is born and receiving underprotective nurture during these years. It

should be noted that there was also an increase in marriage rates in the 1960s and 70s, but the

divorce rates increased relatively more. (S)

Divorce statistics should be further divided into different age groups to find possible differences

in the generational oxytocin levels. The graph below from the U.S. shows that divorce rates have

gone down for younger generations and higher for older generations (S), and it supports the

assumption that oxytocin levels are higher for Millennials and Gen Z. In the 1970s divorce rates

rose for all generations, but divorce rates rates stabilized once the years those couples had

children on average passed the year 1975. For example, a couple aged approx. 40 years in 1990s

were born in 50s, had children in the 70s, and then high rates of divorce in 90s. But a couple

aged 35 years in 2000s were born in the 60s, had children in the 80s, and then about the same

divorce rates than a decade before.

It is therefore important to note that the older generations, whose children were born before the

70s, slowly if ever recovered from the divorce rate boom. But the younger generations did

“recover”, not continuing the trend set by the older generations. The chart implies that higher

breastfeeding rates (higher oxytocin levels) correlate with lower divorce numbers, but the effect

is weaker for generations that are older when oxytocin levels rise for new children. According to

the most recent studies, the total divorce numbers are still going down due to the low divorce

rates among the youngest generations (S) and their marriages are steadier compared to the

older generations (S) which is also an indicator of them having higher oxytocin levels, since

high oxytocin levels promote monogamy (Scheele et al., 2013 /S) and other attributes that

contribute to maintaining a stable marriage. (Schaer et al., 2009 )

It should be noted that divorces have been found to spread through social circles ( McDermott et

al., 2013 ), and since social circles largely consist of people in the same generation, this is a

good example of how generations gain unique social traits through generationally varying

oxytocin levels and how social interaction – through communication in one form or another –

enhances those traits.

2.2.5 Oxytocin and alcohol consumption

Alcohol consumption statistics should reveal changes in historically varying oxytocin levels

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because alcohol and oxytocin have similar effects (Mitchell et al., 2015 ), and oxytocin has been

shown to inhibit the effects and lessen the cravings for alcohol. (Bowen et al., 2015 )(King &

Becker, 2019 ) If these studies are accurate, then low oxytocin levels could lead to higher

alcohol consumption and higher oxytocin levels could lead to lower alcohol consumption in the

population. The Fourth Turning book states the following about per capita alcohol consumption

rates following the 80 year generational cycle: “They begin rising late in a 1st turning, peak near

the end of the 2nd turning, and then begin a decline during the 3rd turning amid growing public

disapproval.” The graph below shows that the 3rd turnings in recent centuries (1830-1850 and

1910-1930) indeed saw large sudden decreases in per capita alcohol consumption.

Per capita alcohol consumption in the US form 1710 to 1970. (S)

Just like with the changes to divorce legislation, the prohibition laws in many Western nations

in the 1910s and 20s display how higher or lower hormone levels have effects on legislation. (S)

Two more statistics are available from the 19th and 20th century, and both show similar

behavior in alcohol consumption: low points of alcohol consumption are in the 1840s and 1920s

when compared to the previous decades in the UK (S)(S) and the Netherlands (S).

There was once again a similar drop in the alcohol consumption 80 years after the low point of

1920s, as roughly the year 2000 was a low point in the U.S. alcohol consumption, preceded by a

high point in the 1980s. (S) Most Western nations show this same pattern of year 2000s having

lower alcohol consumption rates compared to the 1980s. (S) Especially adolescence alcohol

consumption has greatly gone down for the last two decades in the Western nations (S)(S)(S),

while Boomers’ consumption has gone up in several nations. (S)(S) These statistics are directly

in sync with the previously made presumption that the younger generations (Millennials, Gen Z)

have higher oxytocin levels than the older generations (Boomers, Gen X). But the trend for

adolescents should be turning around 2020-2025 according to this the generational hormone

theory, and first signs of this are possibly already showing for instance in Sweden. (S)

All the alcohol statistics presented point to the fact that the Strauss & Howe were correct in their

observations and that the overall alcohol consumption drops sharply once the 3rd generation is

being born. (S) It should also be pointed out that the sudden drops in alcohol consumption rates

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takes about 10 years, just like the breastfeeding rates go up in about 10 years, and some

breastfeeding statistics show quick movement upwards towards the late 1990s like in Norway

and the US.

Dopamine levels should be also taken into account when looking at alcohol consumption rates,

and this is reviewed in chapter 2.3.1. It is presumed that low dopamine levels drive up the alcohol

consumption, which peaks close to the beginning of the 3rd turning (close to the year 1990 in

this cycle), and then starts a sharp decline that ends before the 3rd turning comes to a close.

2.2.6 A model of generational oxytocin levels

Below are the presumed levels of oxytocin on a societal level compiled to a graph. All data points

are not available from all centuries listed, but at this point, are assumed to be similar. The graph

demonstrates the societal effects of oxytocin, which are presumed to be linked to new mothers,

which is why the presumed birth cohort levels can be found by going backwards by about 30

years. (A more detailed explanation on this is located in chapter 2.4.)

Levels at birth can be calculated by going back roughly 30 years from the years listed below. The percentages are only roughassumptions based on the vole study presented in chapter 1.1.

2.3 Historical dopamine and vasopressin levels

2.3.1 Dopamine levels

While oxytocin levels modulate social coherence in the context of family, friends, and other

small-scale social connections, dopamine modulates group coherence in large-scale social

networks. (Pearce et al., 2017 ) Dopamine modulates an individual’s feeling of being a part of a

large-scale social network like a political party, religious group, or a nation. The feeling of

belonging to an in-group is stronger for an individual that has high levels of dopamine, and the

feeling is weaker for an individual that has low levels of dopamine. Therefore a society

experiencing high levels of dopamine would exhibit high levels of group coherence, leading to

higher levels of in-group favoritism and out-group derogation.

Although there is no direct way to measure the brain’s dopamine levels, low dopamine levels

predispose an individual to having learning problems, impulsive and aggressive behavior, and

proneness to substance abuse and addiction. (Chester et al., 2015 )(Leyton & Vezina, 2014 )

(Gold et al., 2014 )(S)(S)(S) Therefore birth cohorts exhibiting these behavioral traits should

indicate low levels of dopamine. Strauss & Howe have noted that birth cohorts from 1961 to 1964

display the kind of behavioral traits mentioned above, even though they have not been able to

connect the traits to low dopamine levels in the 1990s, because back then the effects of

dopamine were not understood as well as they are today.

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The chart from Generations (1991) illustrates how the birth cohorts from the early 1960s farepoorly at school, show high levels of addition to substance use, and exhibit various impulsivebehavioral traits. (S)

As for criminal behavior, the peak in crime statistics occurred 3o years later after the early 1960s

as the 1980s and 90s show a distinctive peak in crime rates in the majority of Western nations,

and the reasons for this still largely remain ‘a mystery’ to researchers who have been studying

the closely concurrent phenomenon in different countries. (Tonry, 2014 )(Lappi-Seppälä &

Lehti, 2014 )(S)(S)

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Rate of violent crime in the US peaked in 1991. (S)

Rate of crime in Canada peaked in 1991. (S)

Rate of crime in the UK peaked in 1995. (S)

The Strauss-Howe generational theory states that a noticeable increase in crime happens during

a 2rd turning, and the crime rates start to drop during the 3rd turning, and they stay relatively

low during a 4th turning (exception: hate crimes usually become more common during a 4th

turning), and the statistics from the current cycle confirm their premises regarding crime at

different phases of the 80 year cycle. Since most of crime is committed by individuals during

young adulthood, it would mean that the lowest levels of dopamine are found in the birth

cohorts born during the 1960s (when the 2nd turning begun).

This is in line with not only with the fact that low dopamine levels result in impulsive manner,

but also as the feeling of social detachment from the larger community presumably increases

with low dopamine levels, it becomes easier for the individual to break the common rules, that

being the written law, and also the unwritten social rules of a society.

And as with the proxy statistics for oxytocin, Russia lags roughly 15 years behind the US in the

crime rate statistics, with the peak being in the 2000s.

Rite of crime in Russia. (S)

These statistics of mid-cycle aggressive behavior are also in line with the observations

regarding many animal populations during the mid-cycle: “animals in high-density phases are

much more aggressive than those in low-density phases.” (Oli, 2019 )(Matthiopoulos et al.,

2002 )(Piertney et al, 2008 )

As for dopamine’s effect on alcohol consumption, chapter 2.2.5 already established the fact that

the Baby Boomers (a 1st generation) have the highest rates of alcohol consumption, but the

statistic below from the UK shows how the birth cohorts from the early 1960s also have the

lowest levels of abstinence.

Birth cohort percentage of men (cubes) and women (triangles) abstainers in the UK. (Menget al., 2013 )

As for dopamine’s effect on learning, looking at SAT scores in the US, it is clear that the birth

cohorts from the early 1960s have the worst test scores, since the SAT test is taken at the age of

17 or 18.

SAT math scores statistic illustrates the poor test results from the birth cohorts ofthe early 1960s. (S)

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The UK statistics show similar results of increasing test scores in the late 1980s and then

reaching top scores around the year 2010. (S)(S) The years 2009-2012 represent the top in the

OECD Pisa test scores in each category that are reading, math, and science. (S) (The OECD is

comprised mainly of European nations. (S)) Combining all these results mean that the worst

performers in school were born close to the year 1960 and the best performers were born close

to the year 1990. It should be noted that dopamine obviously is not the only hormone affecting

educational performance, but it does have an effect on memory, learning, motivation, and

concentration. (S) This means that test results cannot be used very reliably as proxy statistics,

but do correlate with the presumed generational dopamine levels at least to a small degree.

The listed proxy statistics for presumed dopamine levels regarding criminal behavior, alcohol

consumption, and educational performance are put together in the graph below. While it is true

that the test scores reached their peak for birth cohorts born in early 1990s, the teenage alcohol

usage statistics have started to level off only in the recent years, indicating that the birth cohorts

with the highest dopamine levels could be closer to the year 2000. (S)(S)

The percentages are only rough assumptions based on the vole study mentioned in chapter 1.1. Societal effects manifestroughly 25-30 years later after a cohort is born as is presented in the next chapter. (Note: The curve should be slightly sharper,and this will be corrected in an upcoming update…)

2.3.2 Group coherence and territoriality

This chapter presents how varying dopamine levels affect the strength of group coherence and

vasopressin levels affect territoriality. Vasopressin levels are (apparently) not detectable from

historical statistics in a similar way as oxytocin and dopamine, but seasons of heightened

nationalism seem to go hand in hand with increasing group coherence, thus the presumption

that the generational vasopressin levels go hand in hand with the dopamine levels. This

presumption is supported by the Russian vole study, that shows the last year experiencing the

highest levels of vasopressin.

Placing dopamine in the center of human social evolution is actually not a novel idea, since it

has been suggested before. (Previc, 2009 ) In addition, a recent study enforces this idea,

because what sets humans apart from other apes is abnormally high levels of dopamine:

“However, in line with another recent study on gene expression, humans had dramatically more

dopamine in their striatum than apes… Humans also had less acetylcholine, a neurochemical linked to

dominant and territorial behavior, than gorillas or chimpanzees. The combination “is a key difference

that sets apart humans from all other species”… Those differences in neurochemistry may have set in

motion other evolutionary changes, such as the development of monogamy and language in humans…

As human ancestors got better at cooperating, they shared the know-how for making tools and

eventually developed language—all in a feedback loop fueled by surging levels of dopamine.”

(Raghanti et al., 2018 /S/S)

During vole population peak years, that being 2nd and 3rd years, immigration increases,

territory boundaries are reduced, and co-existence with other species of voles increases. (Tähkä

et al., Endocrine aspects of population regulation in the genus Clethrionymus , Mem. Soc. fauna Flora

Fenn., 1984) In human populations, this kind of behavior would mean that the 2nd and 3rd

turnings are more cosmopolitan eras of low nationalism and group coherence, which would be

the years 1970-2010 in the current cycle.

During the last year/quarter of the vole cycle, group coherence and territoriality increase. Group

coherence, territoriality, and nationalism have risen in many Western nations during the past

4th turnings: 1930-1950, 1850-1870, and 1770-1790 have witnessed it, and in 2010-2030 the

same thing is very evidently happening again. Going further in history, during the 4th turning of

1690-1710 there was a movement towards increased centralized power of kings and the Pope,

even though the concept of a nation was not yet largely adopted in Europe. Even the 4th turning

years of 1610-1630 were “nationalistic” and had populistic tendencies (chapter 4.3 has more on

this). These event are taken into account in the graph below, which represents both the

presumed dopamine levels affecting group coherence (levels at birth were presented in the

previous chapter 2.3.1) and presumed vasopressin levels affecting territoriality. The 4th year is

also when the cyclical vole populations see increasing territoriality and decreasing co-existence

with other vole species.

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‘Group coherence and territoriality’ largely reflects the political/ideological uprisings/revolutions, which are often occurringduring or close to the 4th turnings. The percentages are only rough assumptions based on the vole study mentioned in chapter1.1.

To further elaborate the effects of dopamine, the graph below illustrates the effect to group

coherence in a society when the levels of social hormones are either low or high. The circles

represent figurative outer limits of social, ideological and cultural norms. The out-groups left

outside have historically often been immigrants, Jews, and other cultural and ideological

minorities, suspect of ending up as scapegoats for many societal problems when demands for

tighter social coherence increase.

The spots can represent either individuals or groups (depending on the scale).

Strauss & Howe write about tightening social (group) cohesion being a part of a 4th turning and

that keeping good social relations within one’s existing social circles is important, because those

individuals who are shunned outside social circles will end up without much social support as

the social coherence tightens. (More on group coherence and scapegoating in chapter 4.) Quick

examples of increasing group coherence in civic life during the current 4th turning are the “PC

culture” and MeToo-movement. These movements have been about enforcing tightening

unwritten in-group rules, but the new tighter rules have also been enforced through the justice

system, which represents the written rules. Together these written and unwritten rules form an

in-group’s behavioral and ideological boundaries, and these boundaries are tighter in a 4th

turning due to increased group coherence.

The PC culture became mainstream during the 2000s and has become stronger ever since,

evolving into an outrage culture (aka. cancel culture). It began as an movement to tighten in-

group rules to be more inclusive of out-groups, but ever since the ideological spectrum widened

during the 2010s, it became a movement primarily in the left-wing ideological in-group. The

MeToo-movement was founded in 2006, became mainstream in 2017, and spawned a multitude

of other call-out movements aimed at reducing many old behavioral traits that were deemed bad

towards others in an in-group, but were more tolerated during the 2nd and 3rd turnings. The

call-out culture has been spreading through the Western nations quickly, and those who have

not complied with the new social rules have been shunned out of social groups, just like Strauss

& Howe predicted three decades ago.

Another example of this tightening in-group coherence is the destruction of statues that

represent figures from the past that, in their time, have had opinions that are no longer

tolerated at all, like statesmen who were proponents of slavery. Books and other platforms

presenting the opposing side’s ideals may be banned or destroyed. This is the same behavior

that is often witnessed after a war has ended: the winners write the history, and the losing side’s

institutions are molded to represent the winning side’s ideology.

Higher vasopressin levels are associated with nationalism and territoriality. (Caldwell, 2017 )

(S) Territoriality is essentially national in-group defense against out-groups. The two graphs

below represent a simplified expression of higher and lower group coherence (dopamine) and

territoriality (vasopressin) effects in history of the Western cultures, especially in the U.S., and

how it affects group coherence. The idea is not to suggest that hormone levels have caused any

of these historical events, but if dopamine and vasopressin levels have been higher during

certain eras, it might have facilitated some eras and event that display a low/high degree of

group coherence.

The blue line represents presumed high/low dopamine (group coherence, etc.) and vasopressin (territoriality, etc.) effects.

The blue line represents presumed high/low dopamine (group coherence, etc.) and vasopressin (territoriality, etc.) effects.Populist nationalism tends to be higher during the 4th turnings, but there has been populism during other turnings too, like theJacksonian populism in the US, but it occurred only in the US.

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Jacksonian populism in the US, but it occurred only in the US.

When group coherence increases, the demand for institutions grows, since institutions are what

binds the individuals in a society together. Institutions represent feelings of individuals as

moral values in their rules and aims. (More on this in this video from a MIT professor in

psychology.) The Strauss-Howe generational theory states that institutions peak in power

during the 1st turning, which is when the social coherence is also the strongest, before it starts

to decline again. Institutions enforce the common rules through the rule of law, but also

through other means of influence. If the institutions do not represent the general will, or volonté

générale, like Jean-Jacques Rousseau called it (S), there may be a revolt to overturn those

institutions, something that has often happened during the 4th turnings in history. (Chapter 4.2

explains the three basic paths societies usually take during eras of increasing group coherence.)

Institutions are basically “stable, valued, recurring patterns of behavior” . (S) Institutions on

general can be divided into public (government and laws), private (companies and

organizations), and cultural institutions (common traditions and language). Cultural advances

largely rely on functional institutions. When taking a long historical perspective, the largest and

most influential expansive empires and dynasties, with a common culture that is enforced by

institutions, have existed in and spread on from the northern latitudes of 30 to 70, which is also

where the cyclical animal populations exist: the Roman Empire, the British Empire, the Mongol

Empire, the Ottoman Empire, the Spanish Empire, the French Empire, the Achaemenid Empire,

the Macedonian Empire, and the dynasties of Ancient Egypt and China’s to name a few.

There are many ways to sort empires by influence, but here the strength of institutions (including

social institutions like languages and cultural traditions) and expansive growth are given a

priority, since they fit the model of cyclical evolution; eras of low and high social coherence and

territoriality. As for empires in the tropic, the Mayan and Aztec empires were not very

expansive, and African cultures have been quite lacking in institutions that would have made the

empires and their legacy more permanent. And to this day, the majority of sub-Saharan African

nations, and many other nations located in the tropic, have comparatively weak and

dysfunctional institutions. (Nganje, 2015) These kinds of assertions are obviously extremely

speculative, but examples from history do show a tendency for the northern latitudes to have

stronger institutions on general compared to the tropic.

While at first it may seem overly simplifying to equate human populations to other animal

populations, it should be stated that the modulating power of hormones on behavior is strong.

(Oliveira, 2009 ) If humans were able to resist their urges that are due to hormonal activity,

there would probably be no obesity epidemic, addictions like smoking and drugs would be easy

to end, people could override their emotions when making decisions, women would not

experience changes to their mood during different stages of their menstrual cycles, and

individual and group behavior during puberty would be more rational when compared to

behavior before and after puberty. (S)

2.4 Generational social hormone levels

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2.4.1 A model of generational social hormone levels

This (unfinished) chapter contains the proposed model of generational cyclical oxytocin,

dopamine, and vasopressin hormone levels. The graphs are based on previously presented

breastfeeding, maternal age, divorce rate, and alcohol consumption statistics for oxytocin, and

historical observations of increasing and decreasing nationalism (or other manifestations of

high societal in-group cohesion) for dopamine and vasopressin, that is the more aggressive

variant of the social hormones regarding territorial aggression. (Caldwell et al., 2008 )

Since the breastfeeding statistics appear to share a similar historical curve with paternal age and

parenting intensity, it is likely that the size and efficiency are shared between the hypothalamic

neurons secreting hormones to both the brain and blood circulation. Below are all the proxy

statistics combined as has been presented in the previous chapters, now forming a generational

hormone cycle.

Presumed generational hormone levels of parents (the birth cohort levels from roughly 30 years earlier are presented later inthis chapter). The percentages are only rough assumptions based on the vole study mentioned in chapter 1.1.

The generational hormone levels presented in the graph above are presumed to spread among

populations, but the presumed mechanism is not known yet. Research done on couples

demonstrates hormonal synchronization to be an occurring phenomenon (S)(S), as smelling

sweat for instance has been shown to alter hormone levels (Wyart et al., 2007 ), meaning that

sweat works as a chemosignal similarly to pheromones found in other animals like moths and

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mice. This assumption is enhanced by the fact that nasal administration of oxytocin and

vasopressin does increase their behavioral effects, but as hypothalamic hormones are likely

released into brain areas straight from the hypothalamic neurons (S), it could mean that the

hypothalamus is stimulated to secrete oxytocin and vasopressin by the main olfactory cortex (S)

once it detects the chemosignals in the air via the olfactory bulb.

A study done on a red grouse populations showed that injecting testosterone into some males

would result in increased testosterone levels in the other males living in the same area. (Vergara

& Martínes-Padilla, 2012 ) Interestingly enough, the comb size increased on the individuals

receiving injections, but not on the other males, even though they too had elevated testosterone

levels. Increases in testosterone levels increased aggressive behavior, meaning that the

increased testosterone levels that “spread” from the individuals receiving injections had

behavioral but not physiological effects. This would mean that even some individuals or perhaps

those in reproductive ages could be the “primers” that affect the hormone levels of an entire

population. But only regarding behavioral aspects, as the physiological aspects of hormones

would still be determined by the birth hormone levels. This is obviously highly speculative, but

would explain why the ‘social mood’ changes during the 80 year long Strauss-Howe

generational cycle even though the presumed hormone levels received at birth would not change

physiological traits. (This part will most likely be revised when the hypothesis is more

complete…)

In addition, it has been found that during the peak phase in population density in the red grouse

population cycles (marking the middle phases of the population cycle), their comb sizes are at

their largest, accompanied by aggressive behavior (with a minor lag). (Piertney et al, 2008 )

This makes it likely that their testosterone levels are elevated from the beginning of the cycle,

and evidence of this same phenomenon occurring in other populations and human populations

is presented in chapter 2.5.1.

Hypothalamic structural plasticity has been observed for example during the menstrual cycle

and periods of lactation, displaying that the structures inside the hypothalamus are able to

change in size and efficiency quite rapidly. (Baroncini et al., 2010 )(Theodosis et al., 1986 )

Since nasally injected oxytocin and vasopressin increase the behavioral traits of these

hormones, it would be logical to assume that the mechanism is the same with human

interactions: oxytocin in the air reaches the nose and triggers neural oxytocin release into the

brain. It would also explain the occurrence of cross-species adoption, nurture and even lactation

without the adopting “parent” ever being pregnant (Carzon et al., 2019 )(S), and this is

theoretically entirely possible since oxytocin serves the same functions for different mammal

species. (Lactation also requires for example estrogen-mediated prolactin secretion, so the

suggested airborne oxytocin transportation would obviously be only a one part of the suggested

mechanism. (S)) Animals taken out of a population – that is undergoing a cycle – into

laboratory end up developing differently regarding their endocrine system, which suggests that

the development is regulated by a biological mechanism involving proximity, making the

chemosignals a potential candidate.

Another explanation for the generational hormone levels, and currently looking to be the much

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stronger candidate, would be an oscillating developmental cycle, where the year of birth during

the cycle determines the starting hormone levels through the varying hypothalamic neural size

and efficiency, but all generations still undergo the same pattern of fluctuating hormone levels

– only the starting point differs between generations. For the moment, the exact mechanism is

still unknown.

It is theoretically possible that oxytocin and vasopressin secretion from the posterior pituitary

to the bloodstream solely modulates all of the hormone levels (some of which are presented in

the following chapters), since all hormones work as antagonists for other hormones. Oxytocin

inhibits testosterone levels, while vasopressin inhibits growth hormone and promotes

dopamine levels. In this theoretical situation the hypothalamic hormone levels (presented in

chapter 1.2) would oscillate according to the two hormones released from the posterior pituitary.

(Sources to be added…)

Theoretical average birth cohort specific hormone levels in Western nations, backed up bystatistics that are presented in chapter 2. ‘Sex hormones’ represent presumedgonadotropin-releasing hormone levels.The ‘growth hormone’ curve represents thepresumed levels of the growth-hormone-releasing hormone that is secreted by thehypothalamus.

Whatever the mechanism is, it is likely that the biological clock keeping time of years is linked to

the yearly changes in light periods (and possibly changes in light intensity and temperature.

Like previously stated, the cyclical species are almost solely located in the northern 30 to 70

degrees latitude, where the mentioned annual environmental changes are noticeable when

compared to the tropic.

Hours of light each latitude receives annually per day. (S)

Going back to the plasticity of the hypothalamus, there have been studies on human

hypothalamic neurons that secrete oxytocin, and those studies show that age and/or birth

cohort has an impact on the neuron size and efficiency. (Ishunina & Swaab, 1999 ) What these

studies unfortunately do not show is the specific birth cohort/generation information, and this

data would be required to assess if the generational size of neurons coincide with the theoretical

generational hormone cycle. But what the linked study does show is major differences in those

areas of the hypothalamus that both produce and secrete oxytocin and vasopressin. For

example, the older women in this study have over 60% larger volume in vasopressin secreting

neurons than the younger women.

As an further example of generational hormone levels, a 3rd generation show traits of high

oxytocin levels, like higher amounts of prosocial cooperation (De Boer, 2017 ) compared to a

2nd generation, which is ‘abandoned in old age’ according to the Strauss-Howe generational

theory. This is happening likely due to them not creating and fostering as many friendships and

other strong social bonds during their lifespan compared to a 3rd gen. The Strauss-Howe

generational theory states that the 2nd generation is the least social and the 3rd generation is

the most social generation. These phenomena are explained through generational oxytocin

levels, because oxytocin promotes pro-sociality.

Childhood seems to be a time of impact for how an individual’s hormone levels affect the

behavior for the entire lifespan: “Miller and Caldwell (2015) suggested that Oxytocin has an impact

during critical developmental stages for humans in regards to hormonal changes, specifically prenatal,

postnatal and peripubertal stages of life. Manipulation of Oxytocin during these stages could affect

adult behaviour by altering neural structure and function.” (Power, 2015) As young individuals

spend most of their time with children inside their own birth cohorts, like at school and other

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activities, the generational behavioral traits are amplified through social synchrony. (Fitzpatrick

et al., 2018 )

It has been widely speculated why so many couples stayed together during the 1930s Great

Depression, and one popular idea is that couples could not afford to move apart. But the answer

could be very simple: oxytocin levels were high at that time, and because oxytocin is needed to

bind couples, families, and other groups together. The 1970s oil/economic crisis seemed to

cause a lot of divorces, but as the oxytocin levels were presumably at a low point at that time in

history, the stress inducing economic difficulties were efficient in breaking up marriages. And

during the 2007/2008 Great Recession the oxytocin levels were presumably high once again,

thus the divorce rates did not spike due to economic distress.

The changing social mood in the Strauss-Howe generational theory is basically explained by the

changing societal hormonal levels, because hormone levels alter an individual’s mood. For

example, during the 20th century transition from 1st to 2nd turning, when the vasopressin

levels dropped, war protests broke out all over the Western nations in the 1970s, and this

attitude change could also be observed in how war veterans were treated in the Western nations,

suddenly having societal shame cast on them by the general public. The situation has changed

during the 21st century once the average vasopressin levels have presumably once again started

to rise higher. This example demonstrates how the social mood changes to be more supporting

of peace due to generally lower vasopressin levels and vice versa. Therefore the changing social

mood in the Strauss-Howe generational theory can be basically explained by varying social

hormone levels in a society, since hormone levels affect mood.

The average generational hormone levels can be assessed by going backwards about 30 years

from the proxy statistics presented previously.

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Presumed oxytocin, dopamine, and vasopressin levels at birth. The percentages are only rough assumptions based on the volestudy mentioned in chapter 1.1.

On average, at birth:

1st gen has low oxytocin, dopamine, and vasopressin levels;

2nd gen has high oxytocin but low dopamine and vasopressin levels;

3rd gen has high oxytocin, dopamine, and vasopressin levels;

4th gen has low oxytocin but high dopamine and vasopressin levels.

The cyclical pattern of the social hormones resembles the vole hormonal pattern (presented

below) during different phases of their generational population cycle. (Vladimirova et al., 2006

) When comparing the proposed human generational hormone cycle to an animal cycle, a

similar curve can be drawn to the SON portions of the vole cycle. It should be stated again that

percentage levels in the human cycle were assumptions based on the vole study, which is why

the curves look similar. The intention is not to present potentially misleading information, but

only to point out that there is resemblance in the highs and lows between the vole cycle and the

generational hormone cycle of human population, as even by adding both the hormone values of

PVN and SON together would result in a similar graph regarding the high and low points.

Oxytocin and vasopressin levels during the vole population cycle.(Vladimirova et al., 2006 ) The lines are only presumed lines, not actualmeasurements, but instead drawn to illustrate how the hormone levels aresimilar to human birth cohorts’ presumed hormone levels. The humangenerations born during the “peak” in this graph reach adulthood during the4th turning, which coincides with the presumably high vasopressin levels.

2.4.2 Social hormones and political ideology

This and the next chapter (2.4.3) discuss the possible connection between the social hormone

levels and political ideology, since there seems to be noticeable connection between voting

behavior and the presumed social hormone levels. It should be stated that linking ideology and

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the social hormone levels was never a goal for this hypothesis, but that like much of this

hypothesis, this possibility has arisen by chance.

The left vs. right ideological setting is still the fundamental political divider in Western nations,

but especially in the US, where the divide is very clear. Most of the central arguments on

important issues like tax rates, welfare, gun rights, etc. can be drawn from the basic attitude

towards the society: on average, individual rights and responsibilities (aka. self reliance) are more

important for the right-wing voter, and shared rights and responsibilities (aka. the common good)

are more important for the left-wing voter.

It could also be said that even as all humans are capable of empathy, the circle of empathy is

different between the left-wing and right-wing voters: left-wing voters tend to have a circle of

empathy that usually covers minority groups such as immigrants and the least wealthy, and in

comparison, the right-wing voters have a slightly tighter circle of empathy that is usually more

centered on those who are the most beneficial to the society and thus increase the society’s

success when competing against other societies. Although these terms are in no way exclusive to

either side, left-wing voters tend to see themselves as more of citizens of the world and the

right-wing voters tend to see themselves as patriots. (This is an extremely coarse

characterization, and should not be taken as anything else than that.)

Therefore it could be presumed that higher levels of social hormone effects manifest as more

left-leaning ideological behavior, since higher levels of social hormones leads to increased

prosocial behavior. Lower levels of social hormones lead to less social behavior and increased

self reliance, thus the presumed inclination to lean right.

A clear connection between oxytocin and ideological behavior seems to be that oxytocin

increases openness to experiences in individuals (Cardoso et al., 2011 )(Pearce et al., 2019 ), and

simultaneously openness to experience has been found the be the most consistent indicator of

ideology: “Our findings show that, in line with the congruency model of personality, Openness to

Experience is the best and most consistent correlate of political ideology, with politicians high on

Openness to Experience being more likely to be found among the more progressive left-wing political

parties.” (Joly et al., 2018 ) This indicates that higher oxytocin levels may lead to a tendency

towards a left-wing ideology.

Placing a divider so 50% of the cohorts with low/high levels of the social hormones are on both

sides produces the chart below. The presumably right leaning birth cohorts were born

approximately from 1930 to 1970, but there is a small short left leaning cohort born around the

year 1950.

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Presumed oxytocin, dopamine, and vasopressin levels at birth, along with a line witch divides the generations with thelow/high levels of social hormones. Each ideological side is allocated about 40 years, that being 50% of the 80 year cycle. Thepercentages are only rough assumptions based on the vole study mentioned in chapter 1.1.

And by adding a divider, to whenever either the oxytocin or the dopamine & vasopressin curve is

at its lowest value, produces the following graph.

A divider has been added to show what birth cohorts presumably have either the lowest oxytocin or the lowest dopamine &vasopressin levels.

The birth cohort voting preference curve in the graph (above) resembles curve the US voting trend

by birth cohort (below). The voting statistics are very much in line with the presumption that

generations born roughly from 1930 to 1970 tend to vote right, with a small leftist peak close to

1950, and the highest leftist peak is close to 1990 in both graphs.

“The peaks and valleys occur in almost identical locations, strongly suggesting a generationaltrend.” (S) The y-axis represents political alignment on the left vs. right ideological axis, meaningthat the higher the line goes, the more likely individuals in those birth cohorts are to vote left.

If the presumption is correct of social hormone levels affecting generational voting behavior, it

would seem that low vasopressin & dopamine levels may have a stronger effect on the cohort

leaning right than low oxytocin levels. The statistic below is another way of presenting the data,

and it confirms the presumptions regarding birth cohort’s ideological leanings.

Birth cohort specific voting behavior. (S) The birth cohorts in the right column have been added tobetter indicate the birth cohorts and their predominant ideological preference by color.

In addition to birth cohorts displaying ideological preferences, a well known dividing factor

regarding the political spectrum is the “urban vs. rural” divide, since generally urban voters

lean left and rural voters lean right. (S)(S)(S) This implicates that breastfeeding rates are

therefore lower in rural areas, which is confirmed by studies. (S)(S) (Since population density is

lower in rural areas, this leads to speculate if individuals with less efficient oxytocin systems

prefer a rural environment due to them being less socially active compared to individuals with

highly functional oxytocin systems, who are living in urban environments.)

Another possible connection between oxytocin and ideology is that oxytocin increases gaze cues

(for emotional faces) (Tollenaar et al., 2013 ), and since individuals leaning left have been

found to follow gaze cues more than individuals leaning right (Dodd et al., 2010 /S), this adds

to the evidence of high oxytocin levels being possibly connected to a left-wing ideology.

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But can the hormone system actually modulate ideological preferences? The following study

implicates that this is entirely possible.

“The phylogenetically ancient neuropeptide oxytocin has been linked to a plethora of social behaviors.

Here, we argue that the action of oxytocin is not restricted to the downstream level of emotional

responses, but substantially alters higher representations of attitudes and values by exerting a distant

modulatory influence on cortical areas and their reciprocal interplay with subcortical regions and

hormonal systems… Notably, a recent longitudinal epigenetic study detected a positive link between

methylation of the OXT [oxytocin] receptor gene at birth and callous-unemotional traits at age 13,

which corroborates the hypothesis of abnormalities in the oxytocin system as a core element of

developmental pathways to callous-unemotional traits. These findings, together with the relationship

between variations in common polymorphisms of the OXT receptor gene and antisocial behavior, and

high callous-unemotional traits, all point to an involvement of the OXT system in upstream attitudinal

representations… OXT also influences, and interacts with, representations of attitudes and values in

more recently developed cortical regions…” (Hurlemann et al., 2017 )

What is important to note is that the study’s result “…corroborates the hypothesis of abnormalities

in the oxytocin system as a core element of developmental pathways to callous-unemotional traits”,

which are detectable by a persistent pattern of behavior that reflects a disregard for others, and

also a lack of empathy and generally deficient affect. (S) These characterizations best fit the 1st

and 2nd generations in the Strauss-Howe generational theory, and these generations lean

ideologically mostly to right.

According to a recent study, voting is much less rational and more based on emotions than what

has been previously thought to be the case.

“But how should we treat questions of control, free will, and responsibility, given the growing body of

findings about the dubious value of conscious control? An interesting possibility is that humans possess

some automatic control processes for socially relevant thinking and behavior, just as we have

automatic control processes for autonomic regulation. Violent behavior, for example, is likely inhibited

(for most people) through automatic control mechanisms that do not require one to stop and think

about consequences. Emotions may play key roles in such automatic regulation of behavior. Moreover,

the very associative memory processes that sometimes promote bias can work to prevent bias. Changes

in attitudes and associations can be learned through classical or instrumental conditioning, just as

prejudices and bad habits can be unlearned. Attitudes toward same-sex marriage, for example, have

undergone rapid change over the past several decades, and it seems clear this cannot be fully explained

through generational replacement. New beliefs and feelings have been widely adopted, and we believe

it is unlikely this was the result of careful reconsideration of priors. It is much more likely, we think,

that these new attitudes and considerations have formed unconsciously through direct and indirect

experience and an increasingly consistent societal message of support for marriage equality. The most

interesting and important questions about human behavior concern cause, responsibility, and control,

but we do not yet have a satisfactory understanding of the basic underlying mechanisms that give

meaning to these questions. Our research exploring automaticity in political-information processing

and our dual-process theory that roots feeling, thinking, and doing in the associative architecture of

memory is a valuable early step toward a process-valid model of political behavior… As it stands, JQP

[John Q. Public Model of Political Information Processing] paints a very pessimistic view of human

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possibilities. We fear this portrait of “the cognitive monster” may be accurate, but we think control

processes deserve more study. Our gut tells us this last optimism may be rationalization.” (Taber &

Lodge, 2016 )

It should be noted that individual voting behavior is affected by a myriad of different factors

such as who is leading in the polls (S), what images are seen shortly before the voting, etc. ( S)

And like in all decision making, cognitive biases come into play. (S) Things like the ideological

affiliations of college friends can also have an effect on voting behavior, but the effect is quite

small, possibly due to the brain being already quite mature in young adulthood. (S) But even as

these mentioned factors do play a role in voting behavior, they are not that significant when

looking at population-wide statistics over a period of several decades.

2.5 Other hypothalamic hormone levels

2.5.1 Sex hormones

This chapter reviews the effects of the 80 year generational hormone cycle to the human

reproductive system by analyzing generational testosterone and estrogen levels. Most Western

nations have seen low birth rates during the 2010s and infertility is more common than before,

and poor sperm quality is the cause in most cases. (S) Sperm counts have also decreased

significantly during the past decades, over 50% in many countries during the past 50 years.

(Levine et al., 2017 ) This has been accompanied by falling testosterone levels and the younger

generations having less sex. (Travison et al., 2007 )(S)(S)

Phase II generation below, roughly representing human birth cohorts who are in their

reproductive ages during the first half of a 4th turning, shows greatly diminished size in the

lemming gonadotropic cells, which has resulted in less sex hormones and therefore much

smaller testes compared to the phase I and phase III cohorts.

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Phase II in the lemming cycle represents roughly the first half of a 4th turning, and phase IIIrepresents roughly the latter half of a 4th turning. (S)

The same increases in both sex hormone levels and testicular size has been documented in the

cyclical snowshoe hare populations, and the population decline phase is associated with lower

levels of sex hormones. (Davis & Meyer, 1973 ) Human male testicular size is therefore

presumably lower for the age cohorts in reproductive ages during a 4th turning, which would

have a negative effect on sperm quality (Condorelli et al., 2013 ) and testosterone levels, which

is in line with the current situation in the Western nations.

For women, low estrogen levels can produce many of the same symptoms that low testosterone

levels cause for men, like infertility and depression. (Weiss & Clapauch, 2013 )(S) Lower

amounts of estrogen could be the cause for why this 4th turning has many childless women, just

like 80 years ago in the 1930s when many women born in the early 20th century were childless,

which the statistic below of childlessness by year of birth confirms.

Percentage of childless women by year of birth shows a high degree ofsynchrony across many Western nations. (S)

It should be noted that the curves between the countries correlate quite tightly, with Spain

lagging by a few years with its low point, just like with Spain’s paternal age statistics (in chapter

2.2.3) were lagging by about 10 years when compared to statistics from the US and the UK. (This

puts even more weight on the suggestion that Southern Europe has the same generational

hormone cycle as Western Europe does, but they are lagging by about 5-10 years.) Austria and

Switzerland also have very similar statistics regarding childlessness by year of birth with birth

cohorts close to the year 1940 having the least amount of childless women. (Burkimsher &

Zeman, 2017 )

If the statistic above indicates estrogen hormone levels, then it would mean that the birth

cohorts born close to 1980, 1900, 1820, 1740, etc. have the lowest levels of sex hormones, which

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can lead to childlessness. Strauss & Howe note that over five centuries, every 4th turning has

been marked by low birthrates, which correlates with the presented statistics, and also with the

lemming hormone cycle study. (Generations, 1991)

In addition, when looking at birth cohort fertility rates, there is a striking similarity between the

English speaking Western nations presented below. Although the trend has been downward for a

few centuries, there is a clear bump upwards from the 1910 to the 1950 birth cohorts.

Birth cohort total fertility rates for women in Australia, Canada, New Zealand, and the US show verysimilar curves. (S) The peak fertility rate is close to the 1935 birth cohort in the US.

The birth cohorts with the highest levels of sex hormones were presumably born in the 1930s

and 40s, which would help explain the significant baby boom of the 1950s and 60s that is

displayed in the graph below. Spain is once again lagging by about 10 years behind others in this

statistic, just like with the infertility rates and also oxytocin proxy statistics.

Fertility rates in the US, the UK, France (FR), Germany (DE), Switzerland (CH), Sweden (SE),and Spain (ES). (S) The peak is close to 1965.

As for the previous century, the changes in fertility rates are less pronounced in the US and the

UK, that are presumably the two most likely cyclical nations, but the decades around 1880s are

clearly above the trendline in the UK, and in the US, the source statistic does not show much

variance in the 19th century. (S)(S) Many Western nations show a similar trend with the UK, as

the decades after 1880s are generally decades of steep decline in fertility rates, while the

previous decades have been more of a plateau (as a rough generalization). (S)

Putting together the proxy statistics of presumed testosterone and estrogen levels produces the

curve presented below.

Birth cohorts with high fertility/infertility. The effects, both individual and societal, manifest roughly 25-30 years later whenthe cohorts are at reproductive ages. The percentages are only rough assumptions based on the vole study mentioned inchapter 1.1.

But why are there no clear population cycles in the Western nations if there would be a similar

hormone cycle like in the cyclical animal populations? On average, humans today live to be

much older than before (Gurven & Kaplan, 2007 ), and if humans still lived shorter lives like

human populations who lived in the wild/nature, this would be more easily visible in population

numbers. But since most of the Boomers are still alive in 2020, the population numbers have not

plummeted as much.

As for the societal effects of sex hormone levels, the curve in the graph above is roughly in line

with the Strauss-Howe generational theory, which states that the gender gap between the

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reaches it is maximum width during a 1st turning, meaning that the gonadotropic cells are

presumably once again more active and secreting more of sex hormones during that period of

time (societal effects presumably manifest roughly 25-30 years later as the birth cohorts

mature), reflecting phases I and II in the lemming cycle. Higher levels of sex hormones would

thus explain the sexual revolution of the late 60s, when the sex hormone levels were presumably

high, resulting in more sexual activity, especially among the young. (S)(S) Group coherence was

loosening simultaneously, presumably due to decreasing dopamine levels, resulting in looser

unwritten societal rules in the Western nations. (S) According to the Strauss-Howe generational

theory, the gender gap is widest during a 1st turning, and this could be attributed to high levels

of sex hormones especially in the birth cohorts in fertile ages during a 1st turning.

The presumed sex hormone levels are now added to the chart of generational hormone levels

that are presumably received at birth (although especially sex, growth, etc. hormones start to be

secreted more only once puberty hits).

Presumed oxytocin, dopamine, vasopressin, and sex hormone levels at birth. The percentages are only rough assumptionsbased on the vole study mentioned in chapter 1.1. The oxytocin and vasopressin curves have been slightly smoothed in order tobetter represent the oscillating hormone levels.

Apart from issues related to sexual behavior and reproduction, low testosterone levels have

other significant impacts to male health, including a heightened risk for developing metabolic

syndrome, type 2 diabetes, and coronary artery disease. (Goodale et al., 2017 ) Low80

testosterone levels have also been linked to depressive symptoms in men, and according to a

meta-analysis, testosterone treatments have resulted in significant reductions in depressive

symptoms. (Walther et al., 2019 )

2.5.2 Growth and thyroid hormones

Growth-hormone-releasing hormone, that stimulates growth hormone secretion, is secreted

from the hypothalamus, meaning that if it is included in the presumed generationally

fluctuating hypothalamic hormones, this would lead to changing body mass in animal during

population cycles, since higher levels of growth hormone secretion leads to higher body mass.

(Furigo et al., 2019 /S) And this seems to be the case for cyclical animal populations: “An

important biological feature of cyclic populations of voles and lemmings is phase-related changes in

average body mass, with adults in high-density phases being 20–30% heavier than those in low-

density phases of a cycle. This observation, called the “Chitty effect”, is considered to be a ubiquitous

feature of cyclic populations… The Chitty effect is predicted to be most pronounced at the late increase

or peak phase of a population cycle.” (Oli, 1999 )

Placing the hormone level’s peak to the latter part of the peak, that being after the peak in the

sex hormone levels, results in the graph below. Since the average weight in Western nations has

gone significantly up during the last century due to easily available calories and decreasing

physical activity, it is difficult to find proxy data from human populations that could verify the

presumed generational fluctuations in the growth hormone levels. (S)(S)(S)

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Presumed oxytocin, dopamine, vasopressin, and sex hormone levels at birth. The percentages are only rough assumptionsbased on the vole study mentioned in chapter 1.1. The ‘growth hormone’ curve represents the presumed levels of the growth-hormone-releasing hormone that is secreted by the hypothalamus.

The lemming graph in the previous chapter also shows smaller thyrotropic cell area during

phases II and III, which could manifest as increasing prevalence of hypothyroidism among the

population during the past few decades, and this seems to be the case according to studies

conducted in the Western nations. (S) As for hyperthyroidism, the evidence is less certain what

the direction has been during the past few decades. (S) The evidence at this point is still very

scarce, so the thyroid hormones are yet to be placed in the hormone graphs.

3 Societal trends and social hormones

3.1 Current societal trends

This chapter introduces a proposition on how the social hormones presented in chapter 2 may

have population-wide effects in societies: chapter 2 explained the presumed fluctuations in

hormone levels between Western generations, and this chapter presents how the social

hormones possibly affect individual and group behavior. The idea of hormone levels having

effects on a societal level is still quite novel, but neuroscience can be used in this manner not

only to explain individual behavior, but also to explain formation and behavior of 1) groups and

2) institutions. (Stanley & Adolphs, 2013 ) (On how feelings shape institutions and

organizations: short video from a MIT professor in psychology.)

When looking at the current political and ideological trends, it is clear that nationalism,

populism, and xenophobia have been on the rise in the Western cultures for approximately the

last twenty years. Both globalism and multilateralism are increasingly rejected. (S) Ideological

polarizations are getting stronger every year. (S)(S)(S) Social divisions based on ideological

identity can be clearly seen in basically all Western nations today, as two or more sides are

separating from each other, creating ideological rifts. (S)(S) Hate crimes are becoming more

common (S)(S), including anti-Semitism. (S)(S)(S) Many scholars have compared the 2010s to

the 1930s, since many of the same societal effects can be observed to have become more

prevalent during those decades that are 80 years apart.

Continuing listing the current societal trends: the status quo of global(istic) politics is being

challenged at an accelerating pace. (S) Press freedom is increasingly being restricted by state

actors (S)(S), free speech is being restricted by non-state actors ( S), and religious freedoms are

being suppressed. (S) News outlets are increasingly ideologically divided (S), fake news are more

frequent, and lying on behalf of one’s own ideological beliefs (S) is becoming more common.

Not even the scientific community is safe from the effects of the post-truth era. (S)(S)(S)

Most studies and pundits explain the movement towards populist nationalism, and more

generally the polarization of opinions in political and civic life, by explaining that they happen

because of different societal phenomena like mass immigration, economic inequality and social

media platforms that are polarizing opinions by forming echo chambers and allowing the

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distribution of fake news. (S)(S) These phenomena are assumed to create anxieties for the

voters of populist nationalists, and the so called “liberal elites” are said to be out of touch. But

none of the explanations or explanatory models built on these observations can predict or

explain the rise of populist nationalism or the other mentioned phenomena with satisfactory

accuracy, and the accuracy gets even worse when trying to apply these explanatory models to

several or all of the Western nations, or to similar societal situations throughout the history.

Tendencies towards populist nationalism are growing basically in every democratic nation in

Europe, and this movement started well before any big immigration or economic crisis of the

2010s. Nationalism grew as the economic situation in Europe was good and it has kept rising

through the worse economic times. Financial crises do raise populist support for a while, but in a

historical perspective populist support has generally leveled out in about 4 years after a crisis.

(S) It is the same thing with immigration crises: the pace of the rise of nationalism and support

for populist parties has not changed much through the years, not on the far-right or the far-left

end. Nationalism and populism are not the same thing, but nationalistic parties are more often

populist than not, especially on the far-right of the political spectrum.

Populist vote share in Europe from 1998 to 2018. (S)

The overall increasing support for populist nationalism in Europe has been very clear and steady

over the past 20 years. The incremental maps below from 1998 to 2018 illustrate how each

European country has followed its path to the current situation of higher than average support

for populist parties.

Populist vote share in Europe from 1998 to 2018. (S) After these maps were published, nationalists madetheir way to the parliaments of Latvia in October 2018 (S), Estonia in March 2019 (S), and Portugal inOctober 2019 (S). This means that there is not even one European nation without nationalists in theirparliament in 2020.

parliament in 2020.

According to Gini statistics below, economic inequality cannot explain the rise of nationalism

and populism, as income inequality has not changed much in the EU, and has actually gone

down for most countries during the last 20 years. In the U.S. income inequality has risen, but

attempts to raise taxes on the top earners or otherwise level out economic inequality have been

pretty rare even on the left, highlights being the candidacy of Bernie Sanders and movements

against the big banks (and neither can be said to be very much associated with populist

nationalism).

Gini income inequality index from 1988 to 2016. (S)

Gini is not the only indicator that should be looked at, as low interest rates and quantitative

easing by the worlds central banks have had a lifting effect on rent prices in Europe and the U.S.,

which has affected mostly low-income workers and may contribute to the dissent against the so

called “elites”. But still, the economic conditions and employment numbers have generally

gotten better during the last five years, and yet populism has increased at the same time. (S)

Poland is a prime example of a nation that has had record economic success during recent years,

but in spite of this, populist nationalism and xenophobia have risen sharply:

“This is not 1937. Nevertheless, a parallel transformation is taking place in my own time, in the Europe

that I inhabit and in Poland, a country whose citizenship I have acquired. And it is taking place without

the excuse of an economic crisis of the kind Europe suffered in the 1930s. Poland’s economy has been

the most consistently successful in Europe over the past quarter century. Even after the global financial

collapse in 2008, the country saw no recession. What’s more, the refugee wave that has hit other

European countries has not been felt here at all. There are no migrant camps, and there is no Islamist

terrorism, or terrorism of any kind.” (S) But if Poland was undergoing an economic depression

today, the situation would very likely be used as a reason for the current increases in

nationalism and xenophobia. Outside of Europe, Australia is not much different from Poland, as

their uninterrupted economic boom has been going on for almost three decades, and

nationalism is on the rise at the same time as it is in Europe and the U.S. (S)(S)

Social media platforms on the other hand seem to accelerate the divisions between individuals

with diverging ideological stances: “Social media use tends to diversify communication within social

networks by making people aware of what others think and feel about political and social issues. Social

media enhance the perception of difference, and interpersonal contacts in these environments are

typically rated less positively than interpersonal contacts in face-to-face communication.” (S) Moral-

emotional posts tend to spread more effectively on social media platforms (S), and the

platforms do play a role in the increasing polarization, but mainly as a catalyst: “Despite these

limitations, this study has provided evidence that social media contribute to the growth of negative

affect in political communication. Moreover, this negative affect is related to the comparatively high

degree of perceived political disagreement that people encounter in social media settings. Thus, to a

certain extent, perceived disagreement in social media settings has its roots in affective

communication processes.” (S) So if social media is mainly intensifying the current societal

trends, whatever they may be at a certain point in time, what could be the root cause for the

increases in populist nationalism among Western nations?

The generational hormone theory presented here suggests that the studies and pundits blaming

the economic disparities, immigration, social media, and other “usual suspects” for the rise of

populist nationalism are probably correct in their observations of these phenomena occurring at

the same time or before the rise of populist nationalism, but at the same time are fundamentally

incorrect in how these phenomena affect the societal change, and thus cannot build working

models to explain the rise of populist nationalism in detail. This is because these mentioned

societal phenomena are expected to mainly work as catalysts for a generational movement, a

generational cycle to be more precise, which is affecting the rise and fall of nationalism in

Western nations at intervals of roughly 80 years.

It is suggested that these (catalytic) events essentially hide a significant reason for the rise of

xenophobia and populist nationalism, just like the Great Depression of 1930s has often been

claimed to be the main reason for the rise of nationalism and anti-Semitism in pre-WW2

Germany and elsewhere. (S) The goal is to demonstrate that generationally varying levels of

social hormones oxytocin, dopamine, and vasopressin largely modulate the historical increases

and decreases of societal phenomena like populist nationalism and xenophobia.

The generational hormone theory presents that hypothalamic hormone levels undergo large

variances throughout an 80 year cycle, creating behavioral trait differences between

generations, and that the varying social hormone levels create rising tides of nationalism, that

essentially consists of tightening in-group cohesion and territoriality, a phenomenon that

seems to occur every 80 years in many Western nations. In history this era is usually preceded by

roughly four decades of globalism, liberalism and relatively peaceful times. All of these different

eras and generations will be reviewed, but as they have already been presented extensively by

historians William Strauss and Neil Howe in their books Generations and The Fourth Turning

(summaries at Wikipedia and LifeCourse), the larger goal is to review how oxytocin, dopamine,

and vasopressin modulate social behavior and how these hormones are linked to the Strauss-

Howe generational theory of 4 x 20 year generations, an 80 year cycle in total.

Presenting a cyclical theory solely on the basis of biology would be very difficult, because there

are so few longitudinal / multi-generational studies including direct measurements of

hypothalamic hormones. But by reviewing presumed hormone levels through proxy statistics,

like breastfeeding statistics for oxytocin levels, and combining these findings with presumed

hormone modulated behavior in history, especially the observations made by Strauss & Howe,

this combination should reveal a generational hormone cycle if there is one to be found.

3.2 Social hormones and societal group behavior

Oxytocin, dopamine, and vasopressin are the paramount hypothalamic social hormones in

mammals. (S) The larger intent of chapter 3 is to point out that many of the current societal

trends presented in the previous chapter, especially the rise of populist nationalism and its

related phenomena, are presumably created by high levels of oxytocin, dopamine, and

vasopressin in human populations. The human endocrine system is still not completely

understood by science, especially regarding the behavioral aspects, which is why the statements

made here are not presented as anything else than a slice of the current knowledge, and mostly

aimed at building a bridge between hormonal activity and societal phenomena.

As a broad generalization of human behavior, humans are social animals that live and act in groups.

(Young, 2008 )(S) Humans have created extensive tools for communication, science, and

culture, but these are basically extensions of animal behavior, since other species too can

communicate and learn new languages and dialects, they can build tools and do math, and they

can pass on their culture to their offspring. (Whitehead et al., 2019 ) But more importantly, in

addition to animals experiencing the more “apparent” feelings like fear or excitement, animals

have been found to have the “more complex” feelings that humans have, such as empathy,

altruism, grief, contempt, and jealousy to name a few. Hormone levels modulate these feelings

in humans and other animal species.

The standard viewpoints to history concentrates on the societal events and actions taken by

individuals, but the generational hormone theory adds a layer of internal biological

responsiveness in the form of (presumed) generational hormone levels. Hormone levels

modulate individual and group behavior, and also group formation and group coherence; the

larger the hypothalamic neurons that secrete hormones are, the stronger the (hormone specific)

reaction to others and the environment is.

Human behavior essentially consist of the responses of individuals and groups to external

stimuli, and hormone levels modulate these responses because they modulate feelings. Average

hormone levels affect how individuals and groups react to:

1) other individuals;

2) groups;

3) their surroundings/environment.

History will thus be mostly viewed and presented here as group behavior, that being further

divided into in-group and out-group behavior. Typical in-groups are family, friends, gender,

nation, culture, ethnicity, religion, political ideology, etc. Out-groups are basically comprised of

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people belonging to other in-groups than one’s own in-groups. Dopamine modulates large-

scale social network group coherence, whereas oxytocin modulates social coherence in the

context of family, friends, and other small-scale social connections. (Pearce et al., 2017 )

Vasopressin modulates territoriality, but does have other behavioral effects too as is presented

later on.

Looking at history as group behavior is a divergence from the more traditional setting of mainly

analyzing individual leaders and their associates, and how their actions have impacted history.

The intent is not to entirely disregard historical individuals who for example want to advance

their own cause and rise to power by using populist messaging, but instead the generational

hormone theory aims to explain when and why individuals are open, or possibly even inclined,

to receive populist messaging, largely negating the belief that this happens solely due to societal

issues, but instead mostly due to a hormone cycle that’s presumably repeating every 80 years.

3.3 Neural in-group vs. out-group separation

Oxytocin promotes closeness for small-scale social networks, and also promotes defending that

network against those who are different. (S) Oxytocin can deepen the wedge towards “the

others” who think or look different, those who are often outside their own social networks. (De

Dreu et al., 2011 ) Higher oxytocin levels lead to a more active separation between in-group and

out-group, a sorting of “us vs. them”. As an example, the graph below illustrates the

biobehavioral system of how oxytocin affects identification of and behavior towards an

individuals in-group and out-group.

(De Dreu & Kret, 2015 )

This group psychology modulation by oxytocin can turn higher oxytocin (and vasopressin)

levels into higher levels of xenophobia and nationalism. (De Dreu, 2011 )(S) This social

psychology study links in-group division to nationalism: “In explaining differences between

groups, people ascribe the human essence to their in-group and consider out-groups as less human.

This phenomenon, called infra-humanization, occurs outside people’s awareness. Because secondary

emotions (e.g. love, hope, contempt, resentment) are considered uniquely human emotions, people not

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only attribute more secondary emotions to their in-group than to out-groups, but are reluctant to

associate these emotions with out-groups. Moreover, people behave less cooperatively (in terms of

altruism, imitation, and approach) with an out-group member who expresses himself through

secondary emotions… Yet, preliminary results show that subjective essentialism and in-group

identification may mediate the effects of infra-humanization. A connection is made between

nationalism and infra-humanization… We believe that infra-humanization and nationalism are the

two sides of the same coin.” (Leyens et al., 2003 )

The same study also suggests an another path to how nationalism rises: “There is still another

possibility, which may better apply, we believe, to nationalism. Nationalism occurs in situations in

which external forces induce people to consider their in-group and a given out-group as parts of a

common superordinate group.” Both of the suggestions laid out here basically fit the theory of

oxytocin (and vasopressin) related rise of nationalism, the in-group mechanism towards

populism and also the latter mechanism regarding external forces, which could widely be

labeled as populism. Populism is the most efficient way to incite and spread nationalism, and

the tendency for nationalism rises with increased social hormone levels. (It is important to note

that oxytocin stimulates dopamine secretion (Love, 2014 ), which in part increases group

coherence.)

Oxytocin has also been found to increase affection towards the flag of one’s own country, which

is an in-group, which adds to the reasoning that oxytocin (and vasopressin*) increase

nationalism. (Ma et al., 2014 ) A nations flags is essentially an in-group symbol that represents

a territory. *Vasopressin is very similar in structure and can upregulate oxytocin receptors (S) if

in high amounts: “Given the similarity in the structure of OT and AVP, OT can bind to AVP receptors

with a lower affinity compared to OT receptors and vice versa. V1A [receptor] is expressed in the

forebrain and is the receptor that is most often linked to the regulation of social behavior…”. (Andari

et al., 2018 ) Vasopressin is generally known to increase anxiety-like behaviors, stress

responsiveness, aggressiveness, and territoriality. (Carter, 2017 )(S)

On the evolution of cooperation within in-group and hate of out-group: “Although cooperation

between groups is not unusual, most forms of human cooperation are in-group bounded and,

sometimes, motivated by the desire to ward-off and subordinate rivaling out-groups. Building on

evolutionary perspectives and models, we propose that humans evolved a capacity for parochial

cooperation, which entails in-group love: the tendency to cooperate with and extend trust toward

those others who are similar, familiar rather than unfamiliar, and belong to one’s own group; and

out-group hate: a willingness to fight against rivaling out-groups. This chapter reviews our own work,

and that of others, showing that parochial cooperation emerges especially when it benefits

individuals’ within-group reputation, affects one’s within-group status, is more prominent among

individuals with chronic prosocial rather than proself value orientation, and is sustained and

motivated by oxytocin, an evolutionary ancient hypothalamic neuropeptide pivotal in social bonding,

pair–bond formation, and empathic responding. Across the board, findings resonate well with

relatively recent evolutionary theory on (inter)group relations and add to classic theory in social

psychology.” (S)

Other studies show similar results regarding oxytocin and group bias: “Results show that oxytocin

creates intergroup bias because oxytocin motivates in-group favoritism and, to a lesser extent, out-

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group derogation.” (De Dreu et al., 2011 ) A good example of oxytocin’s xenophobic effects is in

the Dutch study on whether you sacrifice a person who has a typical Dutch name, or if you

sacrifice a man with a foreign Muslim name. Increase the person’s oxytocin levels who is

making the choice, and the choice that is made will show more xenophobic tendencies; an

individual will now more likely to sacrifice the man with a Muslim name. (S) The rationalization

by the test subject does not really matter, as it can be pretty much anything, but the changing

end result does matter. And this is what oxytocin can influence; it can change the end result of a

decision that associates ideological and cultural values, no matter the rationalization formed in

the individual’s thoughts.

Oxytocin not only promotes in-group conformity, it also alters perceptions of trust and

fairness, which could further ease the conforming to in-groups opinions: “The results reported

here demonstrate that oxytocin stimulates in-group conformity. When asked to rate novel visual

stimuli on attractiveness and when in-group and out-group members exhibited opposing preferences,

individuals given oxytocin expressed preferences that were closer to those of the in-group than the

out-group. This finding provides novel evidence that oxytocin is involved in influencing people’s

preferences about actual stimuli, complementing earlier work demonstrating that oxytocin alters

perceptions of more abstract concepts, such as generosity, trust, and fairness.” (Stallen et al., 2012 )

In addition to oxytocin altering perceptions, it also produces group-serving dishonesty: “We

report here the results of a double-blind, placebo-controlled experiment showing that the hormone

oxytocin promotes group-serving dishonesty. Compared with participants receiving placebo,

participants receiving oxytocin lied more to benefit their groups, did so quicker, and did so without

expectation of reciprocal dishonesty from their group members… Apparently, oxytocin boosts group-

serving behavior, rather than adherence to general moral codes, a conclusion that fits work showing

that oxytocin sustains and enables social bonding as well as trust and cooperation, especially toward

those belonging to one’s own group. Thus, rather than being a neurohormonal modulator of moral

tendencies and universal cooperation, oxytocin appears to function to serve group interests, whether it

is through parochial cooperation and self-sacrifice, through lashing out against those who threaten

group members, or as shown here, through dishonesty and moral code breaking.” (Shalvi & De Dreu,

2014 )

It should be noted that oxytocin did not promote lying to gain individual benefits in the study,

the lying was done only in order to gain benefits specifically for their own group. But since

oxytocin has been found to ramp up the innate social reasoning skills, it is likely that higher

levels of oxytocin enable more dishonesty without losing the feeling of integrity. (S)

Altruism can be seen as a good force in the human behavior, but it has its limitations that seem

to follow conformity and herd mentality: “Some of the most fundamental questions concerning our

evolutionary origins, our social relations, and the organization of society are centered around issues of

altruism and selfishness. Experimental evidence indicates that human altruism is a powerful force and

is unique in the animal world. However, there is much individual heterogeneity and the interaction

between altruists and selfish individuals is vital to human cooperation. Depending on the

environment, a minority of altruists can force a majority of selfish individuals to cooperate or,

conversely, a few egoists can induce a large number of altruists to defect.” (Fehr & Fischbacher, 2003

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Oxytocin also promotes altruistic punishment: “…our results suggest a different perspective on the

popularly known ‘moral molecule’, as we show that OT [oxytocin], rather than having an effect on

positive emotions, amplifies strong negative emotions (i.e. anger) towards non-cooperators within

small groups… Consistent with the finding that emotions, in addition to rational considerations, work

as a proximate mechanism to induce norm-enforcing behavior, our data suggests that OT might have

an amplifying effect on social emotions, including negative, which ultimately triggers the punishment

of defective behavior and leads to the enforcement of social norms.” (Aydogan et al., 2017 )

These mentioned cooperative models of group behavior have been shown to be evolutionarily

efficient by mathematical and game theory models (Shiramizu & Yamamoto, 2017 ), and it also

important to note that these behavioral cooperative mechanisms have a neurobiological basis

that is innate to humans, and also detectable in how human societies are comprised. (Lewis &

Bates 2010 )(Lewis & Bates 2017 )

3.4 Social hormones and populist nationalism

To sum up the findings in the previous chapter, below is a short list of expected changes in

individual and group behavior when oxytocin and vasopressin levels increase.

1. More nationalism, xenophobia and demands for in-group cohesion.

2. Negative emotions towards in-group non-cooperators.

3. Perceptions of trust and fairness are altered as group-serving lying is promoted, which is

enforced by higher innate social reasoning skills.

4. Infra-humanization of out-groups and willingness to fight out-groups.

Points 1 and 2 are often a big part of populist ideology, point 3 basically lays out the post-truth

aka. fake news era. Points 1-3 of these group behavior changes have been on the rise for the last

20 years or so in the Western nations when compared to the 1990s. Only point 4 is yet to fully

materialize, but there are growing efforts to label Muslims and other culturally differing groups

in the Western nations increasingly as out-groups, and there have been a large number of

terrorist attacks between Muslims and “natives” opposing Islam and its cultural teachings. (S)

(S) The number of hate groups has also increased in the US and the EU. ( S)(S)

Increased oxytocin levels lead to higher levels of empathy ( Geng et al., 2018 ), but since the

separation between in-groups and out-groups is increasing at the same time, this combination

can lead to a “wrong kind” of empathy, as the rising feelings of empathy is directed towards the

tightening in-group, and coupled with vasopressin this empathy can even lead to aggressive

behavior (Buffone & Poulin, 2014 ) towards in-group non-cooperators and out-groups

(explained further in chapter 4). Advocates for populist nationalism use the feelings of empathy

constantly to their advantage in their messaging.

Since higher levels of oxytocin increases anxiety towards unpredictable threats ( Grillon et al.,

2013 ), and vasopressin increases anxiety, populist nationalist leaders gain support by talking

about these in-group and out-group threats by presenting ways to address them straight on.

Many experts on populist nationalism claim that anxiety among populist voters is created by

economic worries, but this does not seem to be the case, as these anxieties are actually created

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through emotions – especially fear:

“Populism peddles a politics of fear—of crime, terrorism, unemployment, economic decline, the loss of

national values and tradition—and asserts that other parties are leading their countries to disaster.

Surveys make clear that populist voters are extremely pessimistic: they believe the past was better than

the present and are extremely anxious about the future. But pessimism has infected Western societies

more generally. A recent PEW survey for example revealed that even though growing percentages of

European citizens view their country’s economic situation as dramatically better than a decade ago,

this has not translated into greater optimism about the future. Indeed, in many European countries

the “experience-expectation” differential has grown: in the Netherlands, Sweden and Germany, for

example, approximately 80 percent or more say the economy is doing well, but less than 40 percent

believe the next generation will be better off than their parents. These views reflect a troubling reality:

particularly in times of change and uncertainty, people’s views are shaped more by emotions than

rationality.” (S)

Populist leaders can therefore gain support through creating/compounding economic anxieties.

As an example, Brexit supporters claimed that exiting EU would be beneficial to the UK economy

(which is quite probably not true), and Donald Trump targeted China (and expressed empathy

towards coal miners in his presidential campaign). Anxieties related to xenophobia seem to

most often be an efficient way of gaining populist votes, but a combination of anxieties towards

immigrants and economic worries seems to be an even more efficient combination for populists

in many instances: “illegal immigrants stealing the jobs and committing crimes” or “selfish

Jews hoarding capital at the top” for example are commonly used. These kinds of combinations

of oxytocin and vasopressin enhanced anxieties have been used in order to make scapegoats and

gain popularity through thousands of years of political history. (S)(S)(S) It should be noted that

scapegoating is a mechanism that is common among social mammal species. (S)

In addition, a 2018 study reveals that higher levels of oxytocin and especially vasopressin flatten

social hierarchy: “OT [oxytocin] reduces differences in social behavior between dominant and

subordinate monkeys, thereby flattening the status hierarchy. OT also increases behavioral synchrony

within a pair. Intranasal delivery of aerosolized AVP [vasopressin] reproduces the effects of OT with

greater efficacy. Remarkably, all behavioral effects are replicated when OT or AVP [vasopressin] is

injected focally into the anterior cingulate gyrus (ACCg), a brain area linked to empathy and other-

regarding behavior.” (Jiang & Platt, 2018 ) The findings could further explain why so many of

the populist leaders achieve success by claiming to be “a man of the people”, and also why the

“liberal elites” and Jews, who are often seen as holding places of power, are increasingly

despised during times of rising populist nationalism. Even though this particular though the

study was done on rhesus monkeys, the social hormones have similar effects primates

(although there are some differences among different species).

Based on all of the presented studies, it can be stated that increased levels of social hormones

may indeed manifest as stronger levels of documented group behavior like in-group favoritism,

out-group homogeneity, and group conformity (i.e. large-scale behavioral synchrony). (Everett

et al., 2015 )(Huang et al., 2019 )(S)(S)

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4 Group division and con ict

4.1 Group division

This (highly unfinished) chapter focuses on the mechanism of growing in-group cleavage

leading up to a division into two camps. Other in-group and out-group social dynamics are also

reviewed. The presumption of increasing oxytocin and vasopressin levels leading to “negative

emotions toward in-group non-cooperators” (reviewed in chapter 3) is tested. Both humans

and chimpanzees are taken a look at, since chimpanzees along with bonobos are the closest

relatives of humans, and because a group split of a chimpanzee community happened in 1972 in

Gombe. (Feldblum et al., 2018 )(S) The split in the chimp community led to a four-year war

between the newly formed chimp groups, a civil war of sorts. Comparing chimp group behavior

to human group behavior should offer insight into how they may show similar patterns related

to increased social hormone levels, including tightening in-groups and increased territorial

behavior.

The slowly growing division in the Gombe chimp social network map from 1970 to 1972 (graphic

on the left) resembles the increasing left vs. right political cleavages in the US from 1994 to 2014

(bottom right), which have progressed in a similar fashion in several Western nations, and

Twitter graphs (top right) help to illustrate how these are comparable to the chimpanzee

division in Gombe: two groups are slowly drifting apart.

Visualizations of increasing group cleavages in chimpanzee and human groups. (S)(S)(S)

The statistic below illustrates grooming intensity to chimps taking sides in Gombe. Oxytocin

levels increase with grooming in primates (S), but only with an existing ( S) social bond partner.

The same effect has been observed with humans: “Holt-Lunstad et al. found that couples engaged

in a program of affiliative touch over a 4-week period resulted in higher post-treatment salivary

oxytocin levels than couples in the non-intervention group…” In addition, “Across mammals, infants

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require physical affiliative contact, whereas in adults proximity may be sufficient [to increase

oxytocin levels]…”. (S)

There were two chimps competing for the alpha male status when the in-group split started to

materialize during 1970, and this occurred during the time of increasing grooming and

presumably increasing oxytocin levels. This in not to imply that the presumed rising oxytocin

levels caused the division, but instead that they facilitated it through increasing polarization of

the two camps supporting different alpha males.

The heavy grooming stage marks the final division (statistic below) in the chimpanzee

community that took place during 1971-1972, as can be seen in the chimp social network graph

above left and the grooming intensity graph below: grooming leads to increasing oxytocin levels

-> sides are being chosen (‘follows’ increase) -> division into two groups (‘arrivals’ and

‘follows’ finish the division) -> leads to a conflict between the two new groups in the end

(vasopressin is also likely involved here).

Grooming intensity by year. (S)

The presumption is that the path is similar with humans: it is the rise of oxytocin and especially

vasopressin levels and increased levels of empathy towards in-group members that increases

the wedge towards non in-group members. This seems be occurring today among Western

nations as the ideological cleavages and polarizations deepen between large-scale social

networks, all the way up to the size of nations.

Even if a nation is very unified so that divisions are not a possibility, there still appears to be

some growing divide among its citizens during a 4th turning, which manifests as the rise of

xenophobia (or even fear/scapegoating/defaming individuals or groups of individuals as

witches, as is explained in chapter 4.2). The ones singled out could be for example an ideological

and/or religious minority, but it seems like there must be an opposite side or scapegoats to

blame for pressing societal problems when social hormone levels are high during a 4th turning.

When nationalism rises there most often is a minority group (or groups) that the populists

target, and thus the ones who belong to that minority group become scapegoats who will be

blamed for many of the most pressing problems a society faces, and these can be real or made up

problems: economic depression or economic inequality, crimes, disease, famine or any other

problem that affects the community as a whole. History shows that it really does not matter who

they are, basically any minority (out-)group can be used as an scapegoat if empathy is high

towards the in-group. (A thorough book on empathy and its pitfalls is ‘Against Empathy: The

Case for Rational Compassion’ by Paul Bloom, professor of psychology and cognitive science at

Yale University.)

Assumably, when social hormone levels rise in human and chimp communities, a similar

pattern repeats with both species: tightening of social networks and singling out “the others”.

For example, when chimp oxytocin levels rise, they start to patrol their borders more. (Samuni

et al., 2017 ) In hamsters vasopressin has been found to increase territorial aggression. ( Young

& Flanagan-Cato, 2012 ) These increased territorial instincts could be compared to increased

human territorial behavior, which is often heightened during eras of high nationalism. Similar

movements have been whitnessed in many European countries as demands to more or less shut

down the borders and decrease/stop immigration have been growing stronger during the past

decase, at least when it comes to the refugees from countries with different cultural values

compared to the traditional values in the nation receiving the immigrants. These immigrants

can be “legal” like in the case of Brexit or “illegal” like in the case of the U.S. border wall debate

(not forgetting the recent bans on immigrants from several predominantly Muslim countries).

In addition, if the chimp alpha male does not show enough empathy towards the in-group

members, they can be removed from their position. (S) This may be the reason for the growing

distrust towards the so called “liberal elites”, who on average support more open borders and

higher levels of immigration than the populist nationalists, thus they may be seen as lacking in

empathy towards the perceived in-group during a 4th turning.

So what exactly could happen in humans when social hormone levels rise and is the pattern

same as with chimps, can demands for group conformity divide a previous relatively coherent

in-group into two or more groups? The holocaust is an obvious example of growing in-group

hatred/division towards (perceived) non-cooperators, and the persecution of Jews begun about

six years prior to any offensive aggression towards neighboring nations. Jews were blamed for

the economic woes as well as many other problems.

The following study explains how increasing oxytocin levels leads to declining morality in these

situations: “Justifications may promote unethical behavior because they constitute a convenient

loophole through which people can gain from immoral behavior and preserve a positive self-image at

the same time. A justification that is widely used is rooted in conformity: Unethical choices become

more permissible because one’s peers are expected to make the same unethical choices. In the current

study, we tested whether an exogenous alteration of conformity led to a lower inclination to adhere to

a widely accepted norm (i.e., honesty) under the pressure of competition. We took advantage of the

well-known effects of intranasally applied oxytocin on affiliation, in-group conformity, and in-group

favoritism in humans. We found that conformity was enhanced by oxytocin, and this enhancement had

a detrimental effect on honesty in a competitive environment but not in a noncompetitive

environment. Our findings contribute to recent evidence showing that competition may lead to

unethical behavior and erode moral values.” (Aydogan et al., 2017 )

Blaming Jews for hoarding the capital during an economic downturn could therefore have led to

declining morality and unethical choices by introducing a “competitive environment” and

through higher levels of empathy towards the own in-group. Oxytocin regulates feelings of

empathy and empathy is the source of aggression according to this study: “This study negates

previous beliefs that characteristics like impulsiveness, trait aggression, trait or state anger trigger

aggression, and shows that, not the personality, but empathic feelings trigger aggression.” (S)

(Buffone & Poulin 2014 ) Lower requirements towards honesty from other in-group members

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(mentioned in the first quote) could have made individuals accept weak arguments to explain

the unethical actions taken towards the Jews while maintaining a feeling of personal integrity.

This effect of oxytocin inducing dishonesty to serve one’s in-group in a competitive

environment would also explain the current post-truth era in politics (S) and science (Iyengar &

Massey, 2018 ) that begun around 2015. Since ideologies have departed so far from the center

out, this could be interpreted as an competitive environment that can induce “detrimental effect

on honesty” into anything that is related to political ideologies, including many scientific areas

like climate change (S), abortion (S), and vaccine resistance (S) (that has actually been linked to

the support for populist parties (S)). Because humans are hardwired to dismiss facts that do not

fit their worldview, the increasing cleavages on issues like climate change are only made worse

by better knowledge regarding the issue, since a larger knowledge base can enhance one’s

ideologically motivated reasoning. (Bolsen et al., 2015 /S)

4.2 Paths of tightening group coherence

This (unfinished) chapter puts the proposed generational hormone theory to test by looking at

an earlier peaks of nationalism, as the early 17th century contains clear signs of populism and

rising feelings of early nationalism. 4th turnings are estimated to have happened roughly every

80 years: 1530-1550 | 1610-1630 | 1690-1710 | 1770-1790 | 1850-70 | 1930-1950 and currently

2010-2030.

The graphs in this chapter coarsely illustrate how tightening group coherence during a 4th

turning leads to different end results depending on the starting point that exists at the ending of

a 3rd turning. This is in line with the Strauss-Howe generational theory: a society’s direction in

a 4th turning is largely dependent on the situation it is in when a 4th turning begins, and that

the beginning is marked by a catalytic event that starts the process towards a new order in the

civic life as well.

Path 1 is the most common path and was explained earlier (chapter 2.3.1). Path 2 presents a

situation where the ideological divides/cleavages are already strong when entering a 4th

turning, thus there is a risk of the divisions eventually splitting the main group into two (or

possibly more) separate in-groups. The division into separate in-groups may eventually

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escalate into a conflict, but this would depend entirely on the contentious societal issues at hand.

In this situation virtually everyone is situated on one side or another, thus scapegoating is rare

because both sides try to garner as much supporters as possible, and the opposing group is

blamed/scapegoated for at least the most pressing societal issues/problems.

But an external threat may also accomplish an unification during a 4th turning even if it is

difficult otherwise, just like the rise of the Nazi Germany mostly suppressed the populist

movements (but not nationalism) in many of the war waging countries during WW2, because

the war efforts required cooperation basically at every level of a society. So path 2 can change

into path 1 if the external threat is strong enough to unify the society.

Path 3 presented below is typical for dictatorships, kingdoms, and monarchies that have

accumulated most if not all of the power to a small elite at the top.

Below are examples of the paths taken regarding the US during the past three 4th turnings.

1) The American Revolutionary War was preceded by path 3. The British were the out-group

(although one third of the American colonists fought on the side of England).

2) The American Civil War was preceded by path 2. There were two distinct in-groups, the North

and the South, and there were virtually no scapegoats apart from the other side.

3) WW2 was preceded by path 1, while communists and fascists were the out-groups/scapegoats,

and this way of thinking continued after the war.

In 2020 it would seem that the current 4th turning paths in the US and the UK are closest to path

2, which is not surprising due to the two-party systems, but the political polarizations in the

2010s have been much stronger compared to the 1930s and the 40s (the previous 4th turning).

This obviously is not to imply that the divisions would eventually manifest as a divide, but the

ideological cleavages have been getting stronger every year, especially in the US. Most of the

Western nations seem to be undergoing path 1.

When group coherence tightens in a society, institutions will be used (or at least tried to be used)

to advance the benefit of the in-group, often to derogate an out-group. The usual targets of this

are the justice system, army leadership, state media, and the schooling system, which are

increasingly subjugated under the ruling party. People leading these institution are often

replaced by individuals who are willing to advance the in-group’s cause, and sometimes by any

means necessary, because anyone who is perceived to advance the in-group’s agenda is often

rewarded with fame and fortune. (This is also true for war heroes, movie stars, and helpers of

the least fortunate inside their own in-group.)

If there are free media organizations, they are silenced if possible, and a good example of this is

what has happened during the recent years in Hungary. If no group can control the media, the

free media tends to polarize into two opposing camps due to consumer group behavior, but

possibly also due to ownership demands. Media tycoons are often highly regarded inside their

in-groups, and they can get even more influence inside their in-group by catering to their

demands. This mobilization of institutions in order to further the current societal causes – what

ever they might be – is what has happened during the 4th turnings in history according to

Strauss & Howe.

4.3 In-group empathy and scapegoating of the out-group

When nationalism rises and the unification is successful (or the society was already unified),

there most often is a minority group or groups that the nationalists target, and the ones who

belong to that minority group become scapegoats who will be blamed for many of the most

pressing problems (real or made up problems) a nation faces: economic depression or economic

inequality, crimes, disease, famine, or any other problem that affects the community negatively.

Because scapegoating has been around for thousands of years and since scapegoating is found

also in other animal species, it seems that it is an innate biological mechanism in humans,

which utilizes the neural in-group vs. out-group setting. (S)

History shows that it really does not matter who the scapegoats are, basically any minority

group can be used as a scapegoat. Since there must be someone to blame, suggests that if a

community is very homogeneous in culture and ethnicity, like the Western European countries

very much were during the 16th and 17th centuries, there can be imaginary scapegoats of

groups/individuals like witches, who were blamed for things like disease or a village losing

crops. (On a sidenote, witch hunts are still happening in modern times for instance in India and

Tanzania.)

Catholic and Protestant churches used witch-hunts to advance the spread of their ideological

views: “Among both Catholics and Protestants, witch-hunting became a prime service for attracting

and appeasing the masses by demonstrating their Satan-fighting prowess… When it comes to winning

people to your side, after all, there’s no better method than stoking fears about an outside threat—and

then assuring them that you, and you alone, offer the best protection.” This means that the church

gave in to populism. In addition, it was very similar to what is happening today with the ideological

battles between political parties: “Similar to how contemporary Republican and Democrat candidates

focus campaign activity in political battlegrounds during elections to attract the loyalty of undecided

voters, historical Catholic and Protestant officials focused witch-trial activity in confessional

battlegrounds during the Reformation and Counter-Reformation to attract the loyalty of undecided

Christians.” (S)

Applying the declining moral standards and tolerance for unethical decisions with rising

oxytocin levels from the previous chapter, the witch hunts may have seemed more reasonable

during times of presumably higher oxytocin levels (higher in-group empathy) than with lower

oxytocin levels (lower in-group empathy). The witch hunts were often justified by claiming they

were done in order to protect the children, and this fits to the idea of rising oxytocin levels

increasing empathy towards the weakest of an in-group. The elderly and war veterans are also

similar groups which are not so much respected during 2nd and 3rd turnings, but gain back

respect during 4th and 1st turnings.

After the witch hunts had peaked in Central Europe, the following Thirty Years’ War ( S) was not

so much of a war between countries but instead between areas of groups which had adopted one

of the two main ideologies; Protestants vs. Catholics. The Thirty Years’ War was fought between

Catholic and Protestant states in Central Europe from 1618 to 1648. The conflicts eventually

drew in the great powers of Europe, resulting in one of the longest, most destructive, and

deadliest conflicts in European history. In addition, concurrently rising nationalism in

Switzerland, Denmark, Sweden, France and the Netherlands also had a role in the escalating

conflict. (S) So populism and nationalism were at play, just like during less than a century before

when Luther’s ideas about religion defined a new in-group, Lutherans, who steered away from

the power of the Pope.

“Beyond that immediate matter of dispute, however, their conflict represented the clash of two

contrasting world views—those of the Renaissance and the Reformation. Erasmus was an

internationalist who sought to establish a borderless Christian union; Luther was a nationalist who

appealed to the patriotism of the German people… For years, they waged a battle of ideas, with each

seeking to win over Europe to his side, but Erasmus’s reformist and universalist creed could not match

Luther’s more emotional and nationalistic one; even some of Erasmus’s closest disciples eventually

defected to Luther’s camp. Erasmus became an increasingly marginal figure, scorned by both

Catholics, for being too critical of the Church, and Lutherans, for being too timid. In a turbulent and

polarized age, he was the archetypal reasonable liberal… In The Complaint of Peace, he decried the

nationalist enmities that were splitting the continent.” (S)

The timing presumably was on the side of Luther, because populist nationalism is high during a

4th turning. This is not to say that Luther was a populist or nationalist, but his ideas seem to

have resonated among to those who did have tendencies towards populist nationalism. (Luther

himself did authorize executions of witches, which may imply that he had populistic tendencies,

although he did believe in witches according to his own writings.)

But can high oxytocin and especially vasopressin levels lead to intergroup violence? Empathy

can drive aggression even when it makes no moral sense according to recent studies. (S) Higher

oxytocin levels lead to increased empathy and lower oxytocin levels lead to reduced empathy

(Andari et al., 2018 )(S) Likewise, test subjects who by genetic differences have higher

sensitivity to oxytocin and vasopressin show greater connection between empathy and

aggression. (S page 195.) It should be noted that aggression and violence are complicated

mechanisms, which to there is no one simple answer to explain them, but higher levels of

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vasopressin heighten the possibility of such states of mind occurring: “There is compelling

evidence from several mammalian species including humans that vasopressin enhances

aggression. The activity of the vasopressin appears linked to the serotonin system providing a

mechanism for enhancing and suppressing aggressive behavior.” (Ferris, 2005 )

The following study deepens the understanding towards how oxytocin and vasopressin create

aggression by utilizing empathy towards one’s in-group:

“Although the idea that people aggress on behalf of others is not new at all, we believe the idea that

empathy can drive aggression absent provocation or injustice to be quite novel… We had specifically

predicted that the effects of empathy on aggression would be accounted for by the actions of the

neurohormones vasopressin and oxytocin. Our finding that variation in vasopressin and oxytocin

receptor genes moderate empathy’s effects supports this prediction. More broadly, a role of these

neurohormones in empathy’s effects is consistent with the possibility that empathy facilitates a broad

array of behaviors—whether kind or aggressive—geared toward benefiting vulnerable others…

Specifically, Study 1 showed that when participants reported feeling higher levels of empathy during a

past episode when a close other was threatened and felt distressed, participants were more likely to

report having aggressed on the close other’s behalf… Similarly, the combination of target distress and

empathy significantly predicted increased empathy-linked aggression for individuals with the GG

genotype of OXTR rs53576, but reduced aggression for those with the AG or AA genotypes. Together,

these results suggest that empathy may have predicted aggression due to its effects on vasopressin and

oxytocin… In sum, the present work represents the first evidence that empathy predicts aggressive

behavior on its own, even independent of provocation, and in conjunction with the empathy-linked

hormones/neuropeptides oxytocin and vasopressin.” (Buffone & Poulin, 2014 )

More on intergroup conflict and how oxytocin regulates it through defensive and cooperative

mechanisms:

“Recent evolutionary models suggest that parochial altruism, the link between in-group favoritism

and the benefit of others at a cost to oneself, is key to understanding the evolution of humans’

cooperative traits and propensity for intergroup violence. Intergroup conflict is ubiquitous across

human societies, repeatedly leading to devastating results of prejudice, war, and genocide. Individuals

contribute to these patterns both by supporting in-group members and acting with hostility toward

the out-group. When such a combination contributes to success in intergroup conflicts, parochial

altruism could have evolved, and biological mechanisms that sustain and promote it are likely

adaptive. One such proposed biological mechanism involves the neuropeptide hormone oxytocin,

previously linked with various aspects of human sociality, particularly the development of mother–

offspring bonds, but also tolerance, coordination, and cooperation between nonkin adults. Owing to its

anxiolytic and prosocial effects, oxytocin is proposed to facilitate cooperation during risk, a mechanism

potentially co-opted from maternal defense circuitry. Intranasal administration of oxytocin enhances

in-group co-operation and trust and out-group defensive, but not offensive, competition in men. This

suggests that oxytocin triggers a “tend and defend” form of parochial altruism, accentuating co-

operative behavior toward the in-group as well as defensive behavior toward out-groups.” (Samuni

et al., 2016 )

Although humans are not the only species capable of group violence, humans are (presumably)

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the only mammals that can belong a group, “us”, consisting also of members they have never

met, making large-scale communities a possibility. In addition, vasopressin enhances the

likelihood of a preemptive strike, which underscores the hormone’s aggressive effects on

human behavior:

“Overall, our study clearly illustrates a role for AVP in human defensive aggression during an

experience of potential resource threat. …animal results endorse the idea that vasopressin, which serves

basic sexual and protective functions, can be coopted to regulate more complicated social behaviors in

species that live in large, complex groups, like humans and monkeys. Although parallel evidence about

humans is still elusive, these earlier studies suggest that neuropeptides may deeply regulate human

social behavior as well. In this sense, investigating those processes will be essential toward better

understanding and possibly regulating various social phenomena in our societies.” (Kawada et al.,

2019 )

Applying these aspects of oxytocin and vasopressin (higher possibility of defensive aggression

and preemptive attacks) to the witch hunts and Confessional Battles show a similar pattern to

what was witnessed before and during the WW2 in Germany for instance, where the separation

of the out-group Jews from the in-group started years before the war (and in the Soviet Union

and Japan during WW2, as war efforts were accompanied by mass killings of non-conforming

in-group members, who were essentially seen as out-group members (S)).

The charts below illustrate that there is a familiar pattern of 1) in-group separation and then

defensive aggression towards the singled out scapegoats (witches) when oxytocin levels are

high, after which comes 2) aggression, possibly preemptive, towards outside threats/out-

groups by rising vasopressin and also dopamine levels. The charts below indicates this path of

behavior in the decades during the European witch hunts leading to the Thirty Years’ War. (S)

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The peak in witch hunts is followed by territorial aggression.

It is important to note that witch hunts are still happening during the 2020s in countries like

India and Tanzania, and the recipe is the same as 500 years ago: the one who is scapegoated is

typically an old lonely woman who lives on the outskirts of the community, and can be seen not

being a part of the in-group that is initiating the scapegoating.

The two Ngram statistics ( S) below illustrates the amplitude of the UK and the US witch hunts

through the usage of word ‘witch’, which spiked in British English and American English books

regularly every 80 years at the beginning of 4th turnings. (S)

The usage of the word ‘witch’ in British English coincides with the peak of the European witch trial activity presented before. Ared pillar marks the beginning of a 4th turning: 1610 … 1690 | 1770 | 1850 | 1930 | 2010.

The American witch hunts were much smaller in size during the 1610s than in Europe ( S), but

they peaked higher during the next cycle when the Salem witch trials began in 1692 at the

beginning of a 4th turning, marking the peak of American witch hunts.

The usage of the word ‘witch’ in American English. A red pillar marks the beginning of a 4th turning: 1610 | 1690 | 1770 …1850 | 1930 | 2010. During the 19th century the concept of ‘a witch’ transferred over to the side of fiction literature (S), butbefore this the books about witches were considered to be non-fiction in nature, even academic, like the Hammer of Witches(S)(S) that was a best-selling book for 200 years, only behind the Bible in sold copies.

The last US witch trials with significance occurred close to 1760, as the graph indicates. ( S) The

generational hormone theory is not about explaining the roots of witch hunts and trials, but it is

important to highlight that these statistical peaks in the history of scapegoating display a

cyclical nature that follows the 80 year Strauss-Howe generational cycle. And in the 2010s the

phenomenon of scapegoating came about once again, just like in the 1610s, as anti-Semitism

started to increase towards the end of the decade seemingly out of nowhere, as most of the acts

against Jews have been perpetrated by individuals, not by organized groups.

5 Initial conclusions

5.1 Possible societal trajectories

To sum up the findings made in this hypothesis, there is now a theoretical framework and also a

number of statistics that are in support of the existence of cyclically varying hormone levels

among the generations in Western nations. Historical proxy statistics of especially oxytocin

indicate this, and proxy statistics of dopamine also back up the theoretical framework. Evidence

is less certain for vasopressin levels at the moment, but the presumed vasopressin levels do

correlate with the rise of populist nationalism today and also during previous centuries,

concurring with the presented 80 year cycle. Even though populist nationalism has had different

ways of manifesting, as structures of countries and also types of available ideologies have varied

through the centuries, it has detectable similarities across centuries. This strongly indicates that

the phenomenon has its roots in biology.

It cannot be emphasized enough that hormone levels impact decision making on an unconscious

level. Hormone levels impact actions and reactions of individuals and groups. This coupled with

generational variances in hormone levels creates the generational traits listed by the Strauss-

Howe generational theory, and gives the traits a biological basis similar to many other cyclical

mammal species. In addition, the generational hormone theory implies that individual and

group behavior of humans is closer to other species than previously thought, because individual

and group decision making is apparently largely influenced by social (and other) hormones on

an unconscious level.

The strength of the generational hormone theory is in the relative simplicity which allows

overlooking individual differences received from genetics and environments by reviewing entire

generations’ traits and actions. When looking at the current societal developments, the

presented generational hormone theory is the only theory that addresses basically all of the

central phenomena related to the rise of populist nationalism like rising feelings of nationalism,

xenophobia (anti-Semitism, anti-Muslim sentiments, etc.), ideological and political

polarization, and group serving lying (aka. post-truth era). The theory also addresses questions

like why these phenomena are occurring today and why they are happening all around the

Western nations – even in those nations that have not experienced major economic or civic

difficulties for over two decades. The theory gives ground to the current slow abandonment of

the “liberal status quo” inside many Western liberal democracies.

The more conventional and traditional viewpoints on history can be seen as “actions leading to

consequences”, and then succeeding actions taken upon these consequences. The example used

in the introductory chapter was the often repeated claim that the Great Depression of the 1930s

largely caused the Nazi party to get to power in the pre-WW2 Germany. But such suggestions do

not explain why the 1970s oil crisis did not cause any nationalistic movements. Obviously there

were other reasons as well for the rise of the Nazi’s to power, such as the Treaty of Versailles,

but such treaties have not commonly led to the rise of nationalism. So the explanation is a soup

of consequences and actions which rarely solely cause large increases in nationalism, but

together they somehow did. But even this does not explain the simultaneous rise of nationalism

and anti-Semitism during the 1930s in other European nations.

Presuming that the generational hormone cycle is at least somewhat accurate, predictions could

be made about the upcoming years in general. But these predictions would obviously be only like

weather forecasts, that combine historical models of past 4th turnings with the current events.

The Fourth Turning book links the turnings to seasons of nature, which is fitting, as the

conditions of the seasons cannot be known beforehand, but the seasons do run their course –

with very familiar and predictable patterns. This is also true regarding the animal population

cycles.

‘Predicting the future’ of human societies has a dubious ring to it, but is it predicting the future

that a pre-pubertal person will likely soon undergo years of increased irritability, mood swings,

and changing sexual behavior? Or is it predicting the future to say that a woman close to her

period may have increased irritability, mood swings, and changing sexual behavior? Or that a

cyclical lemming population at the beginning of the cycle will first become less territorial and

socially coherent for the next two years, and after that more territorial and socially coherent for

the next two years. Presumably, all of these are predetermined hormonal events, calculated by

biological clocks.

History cannot predict the future, but taking (the presumed) varying hormone levels among

human populations into account could provide more background to why historical events have

happened the way they have happened, and also to what direction the current societal issues are

pivoting towards. That being said, if the predictions about the hormone levels are correct, for

the remainder of this 4th turning, the trends listed below will presumably spread and gain

popularity in the Western nations due to increasing feelings of in-group coherence (dopamine)

and territoriality (vasopressin).

1) More populist nationalism and political polarization.

2) More xenophobia and hate crimes in different forms towards out-groups, including hate

speech, and acts of violence are increasingly based on in-group ideologies and identification.

3) Centrist parties continue to lose support.

4) Fake and ideologically influenced news will become increasingly efficient as receptivity for

them increases. Conspiracy theories built around opposing in-group’s activities become more

wide-spread.

5) Institutions and organizations (including companies), both public and private, will be

increasingly demanded to take sides on societal/ideological issues, demands for censorship

increase, boycotts are likely.

6) Large reforms in legislation, including Brexit, become more difficult to pass due to political

polarization.

[APRIL 2020 UPDATE: All of the predictions above have come true on average in the Western

nations, with notable increases in support for populist nationalists, anti-Semitism, and other

societal movements that indicate increasing intergroup cleavages. The current coronavirus

crisis environment will presumably increase stress levels across the Western nations, which

presumably leads to more nationalism and support for populism. International institutions and

organizations will presumably continue to derogate as political support and funding becomes

increasingly hard to find from inside the member nations due to increasing nationalism and

economic turmoil.]

The U.S. will presumably keep turning into a propaganda democracy with two diverging partisan

ideological realities with different sets of facts.

Many European countries will presumably stay on the path on becoming more nationalistic and

the EU will start to malfunction, which would lead to less integration. Formation and

functioning of governments will become increasingly difficult as many mainstream parties

refuse to work with the populist parties, after which some of the populist parties and leaders

may have the possibility to form minority governments or have other paths to power through

the established big parties in a similar manner as Donald Trump did.

More problems for example with(in) Austria, Poland, Hungary, and Italy are to be expected,

more rapidly if there is a recession/depression which would undoubtedly act as a catalyst for the

populist movements. The EU will be blamed by populists for many problems as it is an easy

target, as are other multi-national organizations like the UN and WTO, along with international

treaties from environmental protection to arms treaties (Paris agreement, Schengen Agreement,

nuclear arms treaties, immigration treaties, etc.). Items like a common political solution to the

climate change issue may have to wait as the political and social divisions increase, both inside

and between nations, possibly preventing a global solution from being found and agreed on

until a new status quo is reached in global politics. An economic recession or depression would

very likely increase the “us vs. them” tensions greatly, since “they” (out-groups) are most

often blamed for causing the economic downturn and/or making things worse during it.

5.2 A review of societal actions against populism

If one were to view the rise of populist nationalism as a problem/threat, which depends entirely

on one’s viewpoint, below are suggestions that several pundits have made on “how to solve the

problem of increasing populism”, followed by reasons why they will not work very well

according to the presented theory of continuing rise of nationalist populism.

1. “Europe will soon enter a time of post-populism once the voters realize that the populists can’t

eradicate the pressing societal problems with easy solutions.” Even if the populist governments

cannot solve the problems, they will find ways to blame others for them, like the EU, other

nations, minorities or past liberal policies still hurting the country. These explanations will keep

the populists in power.

2. “More direct democracy will solve the problem of hate against the elites.” This may work for a

while in suppressing the populistic messaging, as it may ease the anxiousness of not having a

voice to change the society, but eventually the direction towards nationalism will continue and

populist agendas will gain popularity again.

3. “Reduce immigration and influx of refugees to suppress populism.” This may also work for a

while, as populistic parties gain power much through the anti-immigrant stances they hold.

Unfortunately this will not solve the problems a nation may already have with the growing

dissent against the minorities that are already in the country.

4. “Reduce socio-economic inequalities to suppress populism.” Emmanuel Macron tried this

recently in France in a quick response to the so called yellow vest protests, and final results are

yet to be seen. This is a slow and possibly costly process overall, likely to be led by tax cuts.

5. “Use economic sanctions for non-compliant EU countries if they suppress democracy, justice system

or free press.” This may prevent some of the more radical plans of some nationalistic leaders, but

will erode trust and cooperation between member nations, driving the EU towards and internal

political crisis. But a crisis inside the EU is to be expected sooner or later, as the parties with

highly nationalistic agendas will likely join forces in the European Parliament against the

parties with the more liberal and globalist views of Europe. If a “union of nationalist parties”

reaches a majority in the European Parliament, the results could be unpredictable. To prevent

this from happening the traditional parties will probably bend to some of the more populistic

demands in order to stay in power, altering Europe’s internal direction and external relations in

the process.

6. “Stop hate speech online and elsewhere with ad campaigns and other messaging.” This article

explains why this suggestion probably would not work:

https://www.psychologytoday.com/us/blog/values-matter/201909/why-stop-bigotry-won-t-

stop-bigotry

5.3 Physiological issues

If the prediction holds true that oxytocin levels among new parents will start to go down during

the 2020s, it is likely that breastfeeding rates and maternal and paternal age will also start to go

downwards. In the 21st century oxytocin is given as a nasal spray at hospital for mothers that are

unable to breastfeed after giving birth, which may skew some statistics from the 21st century.

But there are statistics implicating that breastfeeding rates in some countries like Sweden may

have already started to slowly go downwards after 2005. (Ericson et al., 2016 )

If the predictions about sex hormone levels are correct, fertility and birth rates start to go

upwards during early 2020s and continue that trend during the 2030s. (This chapter will be

expanded at a later time…)

5.4 Evolutionary implications / cyclical evolution

This (unfinished) chapter looks at what could be the evolutionary purpose of the presumed

generational hormone cycle? Based on the studies done on cyclical species and the premises of

this hypothesis, the suggestion is that the cycles 1) drive speciation by creating new populations

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and possibly new subspecies and ultimately new species, and 2) increase gene flow if the

migrants enter an existing population.

Gene flow between cyclical animal populations is increased during the high population

numbers, presumably due to the low dopamine and vasopressin levels, which creates a period

low group coherence and low territoriality, resulting in increased gene flow between populations

through migration. When group coherence and territoriality tighten again towards the end of

the cycle, the coherence of the population is once again tighter, and anyone looking or behaving

too differently from the others may be shunned from the pack (although behavior is always

tightly species dependent). Voles are known to be a highly cyclical species, which may be the

reason why their evolution has been so fast: “The study focuses on 60 species within the vole genus

Microtus, which has evolved in the last 500,000 to 2 million years. This means voles are evolving 60-

100 times faster than the average vertebrate in terms of creating different species.” (Fletcher et al.,

2019 /S)

The gene flow effect would be enhanced by the fact that the cycles are in sync between nearby

cyclical populations (this has been documented to occur at least in vole populations). “During the

peaks, the accumulation of new alleles (i.e., alleles not discovered before within the population) and

the appearance of a homogenous population structure suggest higher migration rates and,

consequently, increased gene flow within the population compared to the crash periods.” (Rikalainen

et al., 2012 ) Another study based on data from seven cyclical lemming population states: “High

genetic variability thus implies high gene flow over a considerable area for lemmings… Examination of

empirical data suggests that high genetic diversity may be the rule rather than the exception in cyclic

populations.” (Ehrich & Jorde, 2005)

It should be noted that during the crash periods of the cycles, the immune system is

compromised in many observed cyclical animal populations, and this has been attributed to high

ACTH secretion levels, which is another commonality between cyclical populations. (Sources to

be added…) This could be natures way of testing which animals have the best immune systems,

and then by artificially creating an evolutionary population “bottleneck” / “founder” effect (S),

where only the survivors will get the reproduce, thus creating a population during the next cycle

that is more resistant to disease, although this may not be the case according to this study:

“However, we did not find a bottleneck signature, that is, heterozygosity excess, in the population after

the crash phases.” (Rikalainen et al., 2012)

Some populations may even go extinct during the phase of low population numbers. (Franklin et

al., 2014 ) There is indeed less genetic diversity in mammal, amphibian, bird, and fish

populations that are not located in the tropic, which in theory could be a result of the proposed

cyclical evolution. (Miraldo et al., 2016 )(Smith et al., 2017 )(Manel et al., 2020 ) (Human

impact does not explain these differences. (Millette et al., 2019 ))

In addition to increasing gene flow between populations, the presumed generational hormone

cycle could potentially be an efficient evolutionary mechanism by creating new species, because

it increases migration into new areas, thus producing new populations. A March 2020 paper has

proven Darwin’s claim of new species forming through the evolution of subspecies to be true:

“The research explored whether subspecies could be considered an early stage of speciation – the

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116 117 118

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formation of a new species. van Holstein said: “The answer was yes.” (S/Van Holstein & Foley, 2020

) Because the animal cycles increase seeking of new habitats, details depending on the

species, it seems logical that the generational hormone cycle mechanism creates new subpecies

that then may evolve into new species as time progresses. The migration phase of the cycles can

be viewed as spreading the DNA into new habitats, which then can evolve into a new kind of

entity through epigenetic effects that the new environment produces.

The Hardy-Weinberg Equilibrium presents a state of very little evolution: when there are no

mutations, mating is random, natural selection is not a factor, populations size is large, and

there is no gene flow. But by constantly changing preference attributes in mating behavior,

natural selection, population size, and gene flow, the theoretical generational hormone cycle

accelerates evolution by breaking the stale behavioral attributes that de-accelerate evolution

(which is the state in non-cyclical populations).

This means that the theoretical generational hormone cycle may accelerate evolution by testing

different physiological and behavioral traits. Since the hormone levels are presumably

fluctuating in waves, all of the birth cohorts have slightly different traits. Natural selection plays

a role after this, as only the animals with the most suitable traits survive and produce offspring.

Another way to express this idea: oscillating hormone levels modulates the development of birth

cohorts differently, which shapes the variation available to natural selection. In theory, the

presumed generational hormone cycle brings out physiological and behavioral extremes in

comparison with a non-cyclical population with less pronounced extremes.

5.5 Unresolved questions

1) The hypothesis could be easily verified by looking at the size of hypothalamic neurons in the

cyclical species’ individuals at the different parts of the cycle by using electron microscopes. The

same tests could be done in the animal populations that experience population explosions. As

for humans, the current imaging devices (MRI) are not accurate enough to see individual

neurons in the brain.

2) The remaining hypothalamic hormones that are yet to be included in this hypothesis are

corticotropin-releasing hormone, growth-hormone-releasing hormone, and somatostatin.

3) Finding historical proxy statistics for vasopressin levels would solidify the premise of the

dopamine and vasopressin hormone level curve.

4) What could be controlling a generational oscillation in the endocrine system? In theory, the

presumed infradian clock could be counting years from the amount of light, seasonal

temperatures, or both.

The most logical answer would be the suprachiasmic nucleus (SCN) that controls the body’s

biological clocks: “Outside of the tropics (where day length remains relatively consistent throughout

the year), the changing photoperiod is a reliable and predictable seasonal signal that presents an

opportunity for organisms to adapt to seasonal changes in factors such as temperature and resource

availability in an anticipatory fashion… The SCN receives input from the retina directed towards its

120

ventrolateral subregion, while its dorsomedial region features numerous direct and indirect

projections to other hypothalamic nuclei controlling homeostatic function and to the rest of the brain.”

(Tackenberg & McMahon, 2018 ) “…the SCN perceives and encodes changes in day length and

drives seasonal changes in downstream pathways and structures…” (Coomans et al., 2014 )

Virtually all cyclical animal populations exist in the area between 30 to 70 degrees northern

latitude, which could be due to these latitudes having strong annual rhythms of nature. The

occurrence and amplitude of the cycles is strongest on the northern latitude 55 (Kendall et al.,

2002 ), which very closely corresponds with the minimum latitude in which nautical twilight

can last all night near the summer solstice. During nautical twilight the illumination is such that

the horizon is still visible even on a moonless night, meaning that it gets very dark even in the

summer (compared to more northern latitudes), but the length of day is still very long

(compared to more southern latitudes). (S) This latitude is where the changes in the length of

day are the most pronounced, while still having a dark period every day of the year, which could

be the explanation why this latitude sees the highest occurrence and amplitude regarding the

cycles.

The tropic (between the Tropic of Cancer and the Tropic of Capricorn), that has very small

annual changes to light periods, has fewer regular population cycles, but instead more

population outbreaks, like huge swarms of grasshoppers. The smaller amount of cyclical

populations could therefore be because there is only little variation in the annual light periods.

This presumption is enhanced by the fact that there apparently are no (primary) population

cycles in populations of nocturnal species. (Sources to be added…)

In addition to the changing photoperiod, light’s wavelength also has an effect on the SCN. ( Wahl

et al., 2019 )(Duffy & Czeisler, 2009 ) In humans, blue light has the largest effect on setting

the SCN’s circadian rhythm. The image below illustrates how the human eye detects different

wavelengths of light.

“As outlined above, light is the key zeitgeber in the circadian system and interacts with the masterclock in the SCN via non-image-forming pathways connecting retina and SCN.” (S)

121

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6

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5) Assuming that the premises presented in this hypothesis are correct, a question remains that

Strauss & Howe pondered in their books: what would the modern history of the Western cultures

look like without the generational cycle? What if the The Hardy-Weinberg Equilibrium remained

stable like it is in non-cyclical populations? What if there weren’t eras of low group coherence

that create high rates of individualism and crime, or eras of high group coherence that create

high rates of nationalism and scapegoating other groups?

The year 2005 is a good reference point: no ideological battles that consume everything in

politics, low levels of populism, relatively good relations between most nations, no large-scale

wars between coalitions, no significant culture of over-selfishness nor ideological groupthink,

and individuals are relatively stress free and reasonably – but not overly – optimistic about the

future. This could be roughly the status quo without the theoretical generational hormone cycle.

On the other hand, where would the Western societies be without eras of high group coherence

that have been associated with such things as the French Revolution and the following century

of forming many European nations? What would the social norms be today without such

breakouts as the sexual revolution of the 1960/70s or the MeToo-movement and other recent

movements against anti-social behaviors? And how much less variance would the cultural life

have without these changes to the social and civic life over centuries? If the main premises of

this hypothesis are accurate, it would offer a novel viewpoint to social evolution of populations.

Could the the strength/amplitude of the presumed wave movements determine the speed of

evolution? This is obviously an essential hypothetical question when looking at cyclical animal

populations, but also when looking at human history, but also a question that cannot be

answered easily. This is obviously not the place to make such an analysis in any meaningful

length, and the topic is extremely speculative, but it is important to note how the generational

cycle could have possibly been active also during previous millenniums.

Hypothesis web-link: https://jannemiettinen.fi/FourthTurning/

Contact: jannem@student.uef.fi / https://www.facebook.com/janne.miettinen

References

1. 1.

Myers JH. Population cycles: generalities, exceptions and remaining mysteries. Proc R Soc B.

Published online March 21, 2018:20172841. doi:10.1098/rspb.2017.2841

2. 2.

Wang H, Nagy JD, Gilg O, Kuang Y. The roles of predator maturation delay and functional

response in determining the periodicity of predator–prey cycles. Mathematical Biosciences.

Published online September 2009:1-10. doi:10.1016/j.mbs.2009.06.004

3. 3.

Krebs CJ. Of lemmings and snowshoe hares: the ecology of northern Canada. Proc R Soc B.

Published online October 27, 2010:481-489. doi:10.1098/rspb.2010.1992

4. 4.

Krebs CJ, Bryant J, Kielland K, et al. What factors determine cyclic amplitude in the snowshoe

hare (Lepus americanus) cycle? Can J Zool . Published online December 2014:1039-1048.

doi:10.1139/cjz-2014-0159

5. 5.

Esper J, Büntgen U, Frank DC, Nievergelt D, Liebhold A. 1200 years of regular outbreaks in

alpine insects. Proc R Soc B. Published online December 12, 2006:671-679.

doi:10.1098/rspb.2006.0191

6. 6.

Kendall, Prendergast, Bjornstad. The macroecology of population dynamics: taxonomic and

biogeographic patterns in population cycles. Ecol Letters. Published online November

1998:160-164. doi:10.1046/j.1461-0248.1998.00037.x

7. 7.

Ehrich D, Schmidt NM, Gauthier G, et al. Documenting lemming population change in the

Arctic: Can we detect trends? Ambio. Published online July 22, 2019:786-800.

doi:10.1007/s13280-019-01198-7

8. 8.

Arshavskaya T, Polenov A, Tkachev A. The hypothalamo-hypophysial system of the

lemming, Dicrostonyx torquatus Pallas. III. Population aspects of neuroendocrine regulation.

Z Mikrosk Anat Forsch. 1989;103(4):627-647.

https://www.ncbi.nlm.nih.gov/pubmed/2683448

9. 9.

Vladimirova EG, Chernigovskaya EV, Danilova OA. Hypothalamo-pituitary neurosecretory

system of the Northern redbacked vole Clethrionomys rutilus in the course of population

cycle. J Evol Biochem Phys . Published online March 2006:208-216.

doi:10.1134/s002209300602013x

10. 10.

Sheriff MJ, Krebs CJ, Boonstra R. From process to pattern: how fluctuating predation risk

impacts the stress axis of snowshoe hares during the 10-year cycle. Oecologia. Published

online January 19, 2011:593-605. doi:10.1007/s00442-011-1907-2

11. 11.

Krebs CJ, Boonstra R, Boutin S. Using experimentation to understand the 10‐year snowshoe

hare cycle in the boreal forest of North America. Wilson K, ed. J Anim Ecol. Published online

July 24, 2017:87-100. doi:10.1111/1365-2656.12720

12. 12.

Lewis GJ, Bates TC. Genetic Evidence for Multiple Biological Mechanisms Underlying In-

Group Favoritism. Psychol Sci. Published online October 25, 2010:1623-1628.

doi:10.1177/0956797610387439

13. 13.

Lewis GJ, Bates TC. The Temporal Stability of In-Group Favoritism Is Mostly Attributable to

Genetic Factors. Social Psychological and Personality Science . Published online June 7,

2017:897-903. doi:10.1177/1948550617699250

14. 14.

Pletzer B, Harris T-A, Scheuringer A, Hidalgo-Lopez E. The cycling brain: menstrual cycle

related fluctuations in hippocampal and fronto-striatal activation and connectivity during

cognitive tasks. Neuropsychopharmacol. Published online June 13, 2019:1867-1875.

doi:10.1038/s41386-019-0435-3

15. 15.

Simonneaux V, Bahougne T. A Multi-Oscillatory Circadian System Times Female

Reproduction. Front Endocrinol. Published online October 20, 2015.

doi:10.3389/fendo.2015.00157

16. 16.

Caldwell HK, Albers HE. Oxytocin, Vasopressin, and the Motivational Forces that Drive Social

Behaviors. In: Behavioral Neuroscience of Motivation. Springer International Publishing;

2015:51-103. doi:10.1007/7854_2015_390

17. 17.

MacLean EL, Gesquiere LR, Gruen ME, Sherman BL, Martin WL, Carter CS. Endogenous

Oxytocin, Vasopressin, and Aggression in Domestic Dogs. Front Psychol. Published online

September 27, 2017. doi:10.3389/fpsyg.2017.01613

18. 18.

Neumann ID, Landgraf R. Balance of brain oxytocin and vasopressin: implications for

anxiety, depression, and social behaviors. Trends in Neurosciences. Published online November

2012:649-659. doi:10.1016/j.tins.2012.08.004

19. 19.

Sachs ME, Ellis RJ, Schlaug G, Loui P. Brain connectivity reflects human aesthetic responses

to music. Social Cognitive and Affective Neuroscience. Published online March 10, 2016:884-891.

doi:10.1093/scan/nsw009

20. 20.

Rajamani KT, Wagner S, Grinevich V, Harony-Nicolas H. Oxytocin as a Modulator of Synaptic

Plasticity: Implications for Neurodevelopmental Disorders. Front Synaptic Neurosci. Published

online June 19, 2018. doi:10.3389/fnsyn.2018.00017

21. 21.

Fowden AL, Forhead AJ. Hormones as epigenetic signals in developmental programming.

Experimental Physiology. Published online May 14, 2009:607-625.

doi:10.1113/expphysiol.2008.046359

22. 22.

Crawley JN. Behavioral Phenotyping Strategies for Mutant Mice. Neuron. Published online

March 2008:809-818. doi:10.1016/j.neuron.2008.03.001

23. 23.

Gordon I, Zagoory-Sharon O, Leckman JF, Feldman R. Oxytocin and the Development of

Parenting in Humans. Biological Psychiatry. Published online August 2010:377-382.

doi:10.1016/j.biopsych.2010.02.005

24. 24.

Dotti Sani GM, Treas J. Educational Gradients in Parents’ Child-Care Time Across Countries,

1965-2012. Fam Relat. Published online April 19, 2016:1083-1096. doi:10.1111/jomf.12305

25. 25.

Augustine RA, Ladyman SR, Bouwer GT, et al. Prolactin regulation of oxytocin neurone

activity in pregnancy and lactation. J Physiol. Published online March 23, 2017:3591-3605.

doi:10.1113/jp273712

26. 26.

Scott V, Brown CH. Beyond the GnRH Axis: Kisspeptin Regulation of the Oxytocin System in

Pregnancy and Lactation. In: Advances in Experimental Medicine and Biology . Springer New

York; 2013:201-218. doi:10.1007/978-1-4614-6199-9_10

27. 27.

Ryan AS. The Resurgence of Breastfeeding in the United States. PEDIATRICS. Published online

April 1, 1997:e12-e12. doi:10.1542/peds.99.4.e12

28. 28.

Inoue M, Binns CW, Otsuka K, Jimba M, Matsubara M. Infant feeding practices and

breastfeeding duration in Japan: A review. Int Breastfeed J. Published online 2012:15.

doi:10.1186/1746-4358-7-15

29. 29.

Nutrition During Lactation . National Academies Press; 1991. doi:10.17226/1577

30. 30.

BLANKS A. The role of oxytocin in parturition. BJOG: An International Journal of Obstetrics and

Gynaecology. Published online April 2003:46-51. doi:10.1016/s1470-0328(03)00024-7

31. 31.

Hobbs AJ, Mannion CA, McDonald SW, Brockway M, Tough SC. The impact of caesarean

section on breastfeeding initiation, duration and difficulties in the first four months

postpartum. BMC Pregnancy Childbirth. Published online April 26, 2016. doi:10.1186/s12884-

016-0876-1

32. 32.

Smith LJ. Impact of Birthing Practices on the Breastfeeding Dyad. Journal of Midwifery &

Women’s Health. Published online November 12, 2007:621-630.

doi:10.1016/j.jmwh.2007.07.019

33. 33.

Erickson EN, Carter CS, Emeis CL. Oxytocin, Vasopressin and Prolactin in New Breastfeeding

Mothers: Relationship to Clinical Characteristics and Infant Weight Loss. J Hum Lact .

Published online April 29, 2019:136-145. doi:10.1177/0890334419838225

34. 34.

Erlinge S, Hasselquist D, Svensson M, Frodin P, Nilsson P. Reproductive behaviour of female

Siberian lemmings during the increase and peak phase of the lemming cycle. Oecologia.

Published online May 3, 2000:200-207. doi:10.1007/s004420051006

35. 35.

Lui C, Cui X, Wang Y, You Z, Xu D. Association between neuropeptide oxytocin and male

infertility. J Assist Reprod Genet . Published online August 14, 2010:525-531.

doi:10.1007/s10815-010-9451-2

36. 36.

Sunahara CS, Zelkowitz P, Bolger N, et al. Maternal oxytocin predicts relationship survival

during the perinatal transition period: Preliminary evidence. International Journal of

Psychophysiology. Published online February 2019:33-38. doi:10.1016/j.ijpsycho.2018.04.009

37. 37.

Scheele D, Wille A, Kendrick KM, et al. Oxytocin enhances brain reward system responses in

men viewing the face of their female partner. Proceedings of the National Academy of Sciences .

Published online November 25, 2013:20308-20313. doi:10.1073/pnas.1314190110

38. 38.

Ditzen B, Schaer M, Gabriel B, Bodenmann G, Ehlert U, Heinrichs M. Intranasal Oxytocin

Increases Positive Communication and Reduces Cortisol Levels During Couple Conflict.

Biological Psychiatry. Published online May 2009:728-731. doi:10.1016/j.biopsych.2008.10.011

39. 39.

McDermott R, Fowler JH, Christakis NA. Breaking Up Is Hard to Do, Unless Everyone Else Is

Doing It Too: Social Network Effects on Divorce in a Longitudinal Sample. Social Forces.

Published online October 8, 2013:491-519. doi:10.1093/sf/sot096

40. 40.

Mitchell IJ, Gillespie SM, Abu-Akel A. Similar effects of intranasal oxytocin administration

and acute alcohol consumption on socio-cognitions, emotions and behaviour: Implications

for the mechanisms of action. Neuroscience & Biobehavioral Reviews. Published online August

2015:98-106. doi:10.1016/j.neubiorev.2015.04.018

41. 41.

Bowen MT, Peters ST, Absalom N, Chebib M, Neumann ID, McGregor IS. Oxytocin prevents

ethanol actions at δ subunit-containing GABAA receptors and attenuates ethanol-induced

motor impairment in rats. Proc Natl Acad Sci USA. Published online February 23, 2015:3104-

3109. doi:10.1073/pnas.1416900112

42. 42.

King CE, Becker HC. Oxytocin attenuates stress-induced reinstatement of alcohol seeking

behavior in male and female mice. Psychopharmacology. Published online March 28,

2019:2613-2622. doi:10.1007/s00213-019-05233-z

43. 43.

Pearce E, Wlodarski R, Machin A, Dunbar RIM. Variation in the β-endorphin, oxytocin, and

dopamine receptor genes is associated with different dimensions of human sociality. Proc

Natl Acad Sci USA. Published online May 1, 2017:5300-5305. doi:10.1073/pnas.1700712114

44. 44.

Chester DS, DeWall CN, Derefinko KJ, et al. Looking for reward in all the wrong places:

dopamine receptor gene polymorphisms indirectly affect aggression through sensation-

seeking. Social Neuroscience. Published online December 7, 2015:487-494.

doi:10.1080/17470919.2015.1119191

45. 45.

Leyton M, Vezina P. Dopamine ups and downs in vulnerability to addictions: a

neurodevelopmental model. Trends in Pharmacological Sciences. Published online June

2014:268-276. doi:10.1016/j.tips.2014.04.002

46. 46.

Gold MS, Blum K, Oscar–Berman M, Braverman ER. Low Dopamine Function in Attention

Deficit/Hyperactivity Disorder: Should Genotyping Signify Early Diagnosis in Children?

Postgraduate Medicine. Published online January 2014:153-177. doi:10.3810/pgm.2014.01.2735

47. 47.

Tonry M. Why Crime Rates Are Falling throughout the Western World. Crime and Justice.

Published online September 2014:1-63. doi:10.1086/678181

48. 48.

Lappi-Seppälä T, Lehti M. Cross-Comparative Perspectives on Global Homicide Trends.

Crime and Justice. Published online September 2014:135-230. doi:10.1086/677979

49. 49.

Oli MK. Population cycles in voles and lemmings: state of the science and future directions.

Mam Rev. Published online May 10, 2019:226-239. doi:10.1111/mam.12156

50. 50.

Matthiopoulos J, Moss R, Lambin X. The kin facilitation hypothesis for red grouse population

cycles: territorial dynamics of the family cluster. Ecological Modelling. Published online

January 2002:291-307. doi:10.1016/s0304-3800(01)00420-3

51. 51.

PIERTNEY SB, LAMBIN X, MACCOLL ADC, et al. Temporal changes in kin structure through a

population cycle in a territorial bird, the red grouse Lagopus lagopus scoticus. Molecular

Ecology. Published online April 22, 2008:2544-2551. doi:10.1111/j.1365-294x.2008.03778.x

52. 52.

Meng Y, Holmes J, Hill-McManus D, Brennan A, Meier PS. Trend analysis and modelling of

gender-specific age, period and birth cohort effects on alcohol abstention and consumption

level for drinkers in Great Britain using the General Lifestyle Survey 1984-2009. Addiction.

Published online September 13, 2013:206-215. doi:10.1111/add.12330

53. 53.

Previc FH. The Dopaminergic Mind in Human Evolution and History. Published online 2009.

doi:10.1017/cbo9780511581366

54. 54.

Raghanti MA, Edler MK, Stephenson AR, et al. A neurochemical hypothesis for the origin of

hominids. Proc Natl Acad Sci USA. Published online January 22, 2018:E1108-E1116.

doi:10.1073/pnas.1719666115

55. 55.

Caldwell HK. Oxytocin and Vasopressin: Powerful Regulators of Social Behavior.

Neuroscientist. Published online May 11, 2017:517-528. doi:10.1177/1073858417708284

56. 56.

Oliveira RF. Social behavior in context: Hormonal modulation of behavioral plasticity and

social competence. Integrative and Comparative Biology . Published online July 21, 2009:423-

440. doi:10.1093/icb/icp055

57. 57.

Caldwell HK, Lee H-J, Macbeth AH, Young WS III. Vasopressin: Behavioral roles of an

“original” neuropeptide. Progress in Neurobiology. Published online January 2008:1-24.

doi:10.1016/j.pneurobio.2007.10.007

58. 58.

Wyart C, Webster WW, Chen JH, et al. Smelling a Single Component of Male Sweat Alters

Levels of Cortisol in Women. Journal of Neuroscience. Published online February 7, 2007:1261-

1265. doi:10.1523/jneurosci.4430-06.2007

59. 59.

Vergara P, Martínez-Padilla J. Social context decouples the relationship between a sexual

ornament and testosterone levels in a male wild bird. Hormones and Behavior. Published

online September 2012:407-412. doi:10.1016/j.yhbeh.2012.07.007

60. 60.

Baroncini M, Jissendi P, Catteau-Jonard S, et al. Sex steroid hormones-related structural

plasticity in the human hypothalamus. NeuroImage. Published online April 2010:428-433.

doi:10.1016/j.neuroimage.2009.11.074

61. 61.

Theodosis DT, Chapman DB, Montagnese C, Poulain DA, Morris JF. Structural plasticity in the

hypothalamic supraoptic nucleus at lactation affects oxytocin-, but not vasopressin-

secreting neurones. Neuroscience. Published online March 1986:661-678. doi:10.1016/0306-

4522(86)90038-2

62. 62.

Carzon P, Delfour F, Dudzinski K, Oremus M, Clua É. Cross‐genus adoptions in delphinids:

One example with taxonomic discussion. Ethology. Published online June 25, 2019:669-676.

doi:10.1111/eth.12916

63. 63.

Ishunina TA, Swaab DF. Vasopressin and Oxytocin Neurons of the Human Supraoptic and

Paraventricular Nucleus; Size Changes in Relation to Age and Sex. The Journal of Clinical

Endocrinology & Metabolism. Published online December 1999:4637-4644.

doi:10.1210/jcem.84.12.6187

64. 64.

de Boer M, Kokal I, Blokpoel M, et al. Oxytocin modulates human communication by

enhancing cognitive exploration. Psychoneuroendocrinology. Published online December

2017:64-72. doi:10.1016/j.psyneuen.2017.09.010

65. 65.

Fitzpatrick P, Frazier JA, Cochran D, Mitchell T, Coleman C, Schmidt RC. Relationship

Between Theory of Mind, Emotion Recognition, and Social Synchrony in Adolescents With

and Without Autism. Front Psychol. Published online July 31, 2018.

doi:10.3389/fpsyg.2018.01337

66. 66.

Cardoso C, Ellenbogen MA, Linnen A-M. Acute intranasal oxytocin improves positive self-

perceptions of personality. Psychopharmacology. Published online October 20, 2011:741-749.

doi:10.1007/s00213-011-2527-6

67. 67.

Pearce E, Wlodarski R, Machin A, Dunbar RIM. Genetic Influences on Social Relationships:

Sex Differences in the Mediating Role of Personality and Social Cognition. Adaptive Human

Behavior and Physiology. Published online November 26, 2019:331-351. doi:10.1007/s40750-

019-00120-5

68. 68.

Joly JK, Hofmans J, Loewen P. Personality and Party Ideology Among Politicians. A Closer

Look at Political Elites From Canada and Belgium. Front Psychol. Published online April 17,

2018. doi:10.3389/fpsyg.2018.00552

69. 69.

Tollenaar MS, Chatzimanoli M, van der Wee NJA, Putman P. Enhanced orienting of attention

in response to emotional gaze cues after oxytocin administration in healthy young men.

Psychoneuroendocrinology. Published online September 2013:1797-1802.

doi:10.1016/j.psyneuen.2013.02.018

70. 70.

Dodd MD, Hibbing JR, Smith KB. The politics of attention: gaze-cuing effects are moderated

by political temperament. Atten Percept Psychophys. Published online November 4, 2010:24-

29. doi:10.3758/s13414-010-0001-x

71. 71.

Hurlemann R, Marsh N, Schultz J, Scheele D. Oxytocin shapes the priorities and neural

representations of attitudes and values. Behav Brain Sci. Published online 2017.

doi:10.1017/s0140525x16000807

72. 72.

Taber CS, Lodge M. The Illusion of Choice in Democratic Politics: The Unconscious Impact of

Motivated Political Reasoning. Political Psychology. Published online January 22, 2016:61-85.

doi:10.1111/pops.12321

73. 73.

Levine H, Jørgensen N, Martino-Andrade A, et al. Temporal trends in sperm count: a

systematic review and meta-regression analysis. Human Reproduction Update. Published

online July 25, 2017:646-659. doi:10.1093/humupd/dmx022

74. 74.

Travison TG, Araujo AB, O’Donnell AB, Kupelian V, McKinlay JB. A Population-Level Decline

in Serum Testosterone Levels in American Men. The Journal of Clinical Endocrinology &

Metabolism. Published online January 1, 2007:196-202. doi:10.1210/jc.2006-1375

75. 75.

Davis GJ, Meyer RK. FSH and LH in the snowshoe hare during the increasing phase of the 10-

year cycle. General and Comparative Endocrinology . Published online February 1973:53-60.

doi:10.1016/0016-6480(73)90129-9

76. 76.

Condorelli R, Calogero AE, La Vignera S. Relationship between Testicular Volume and

Conventional or Nonconventional Sperm Parameters. International Journal of Endocrinology .

Published online 2013:1-6. doi:10.1155/2013/145792

77. 77.

Weiss RV, Clapauch R. Female infertility of endocrine origin. Arq Bras Endocrinol Metab.

Published online March 2014:144-152. doi:10.1590/0004-2730000003021

78. 78.

Burkimsher M, Zeman K. Childlessness in Switzerland and Austria. In: Demographic Research

Monographs. Springer International Publishing; 2017:115-137. doi:10.1007/978-3-319-

44667-7_6

79. 79.

Gurven M, Kaplan H. Longevity Among Hunter- Gatherers: A Cross-Cultural Examination.

Population & Development Review. Published online June 2007:321-365. doi:10.1111/j.1728-

4457.2007.00171.x

80. 80.

Goodale T, Sadhu A, Petak S, Robbins R. Testosterone and the Heart. Methodist DeBakey

Cardiovascular Journal. Published online April 2017:68-72. doi:10.14797/mdcj-13-2-68

81. 81.

Walther A, Breidenstein J, Miller R. Association of Testosterone Treatment With Alleviation of

Depressive Symptoms in Men. JAMA Psychiatry. Published online January 1, 2019:31.

doi:10.1001/jamapsychiatry.2018.2734

82. 82.

Furigo IC, Teixeira PDS, de Souza GO, et al. Growth hormone regulates neuroendocrine

responses to weight loss via AgRP neurons. Nat Commun. Published online February 8, 2019.

doi:10.1038/s41467-019-08607-1

83. 83.

Oli MK. The Chitty Effect: A Consequence of Dynamic Energy Allocation in a Fluctuating

Environment. Theoretical Population Biology. Published online December 1999:293-300.

doi:10.1006/tpbi.1999.1427

84. 84.

Stanley DA, Adolphs R. Toward a Neural Basis for Social Behavior. Neuron. Published online

October 2013:816-826. doi:10.1016/j.neuron.2013.10.038

85. 85.

Young S. The neurobiology of human social behaviour: an important but neglected topic. J

Psychiatry Neurosci. 2008;33(5):391-392. https://www.ncbi.nlm.nih.gov/pubmed/18787656

86. 86.

Whitehead H, Laland KN, Rendell L, Thorogood R, Whiten A. The reach of gene–culture

coevolution in animals. Nat Commun. Published online June 3, 2019. doi:10.1038/s41467-019-

10293-y

87. 87.

De Dreu CKW, Greer LL, Van Kleef GA, Shalvi S, Handgraaf MJJ. Oxytocin promotes human

ethnocentrism. Proceedings of the National Academy of Sciences . Published online January 10,

2011:1262-1266. doi:10.1073/pnas.1015316108

88. 88.

De Dreu CKW, Kret ME. Oxytocin Conditions Intergroup Relations Through Upregulated In-

Group Empathy, Cooperation, Conformity, and Defense. Biological Psychiatry. Published

online February 2016:165-173. doi:10.1016/j.biopsych.2015.03.020

89. 89.

Leyens J-P, Cortes B, Demoulin S, et al. Emotional prejudice, essentialism, and nationalism

The 2002 Tajfel lecture. Eur J Soc Psychol. Published online 2003:703-717. doi:10.1002/ejsp.170

90. 90.

Love TM. Oxytocin, motivation and the role of dopamine. Pharmacology Biochemistry and

Behavior. Published online April 2014:49-60. doi:10.1016/j.pbb.2013.06.011

91. 91.

Ma X, Luo L, Geng Y, Zhao W, Zhang Q, Kendrick KM. Oxytocin increases liking for a

country’s people and national flag but not for other cultural symbols or consumer products.

Front Behav Neurosci . Published online August 5, 2014. doi:10.3389/fnbeh.2014.00266

92. 92.

Andari E, Hurlemann R, Young L. A Precision Medicine Approach to Oxytocin Trials. Curr Top

Behav Neurosci. 2018;35:559-590. doi:10.1007/7854_2017_29

93. 93.

Carter CS. The Oxytocin–Vasopressin Pathway in the Context of Love and Fear. Front

Endocrinol. Published online December 22, 2017. doi:10.3389/fendo.2017.00356

94. 94.

Stallen M, De Dreu CKW, Shalvi S, Smidts A, Sanfey AG. The Herding Hormone. Psychol Sci.

Published online September 18, 2012:1288-1292. doi:10.1177/0956797612446026

95. 95.

Shalvi S, De Dreu CKW. Oxytocin promotes group-serving dishonesty. Proceedings of the

National Academy of Sciences. Published online March 31, 2014:5503-5507.

doi:10.1073/pnas.1400724111

96. 96.

Fehr E, Fischbacher U. The nature of human altruism. Nature. Published online October

2003:785-791. doi:10.1038/nature02043

97. 97.

Aydogan G, Furtner NC, Kern B, Jobst A, Müller N, Kocher MG. Oxytocin promotes altruistic

punishment. Social Cognitive and Affective Neuroscience. Published online August 29,

2017:1740-1747. doi:10.1093/scan/nsx101

98. 98.

Shiramizu VKM, Yamamoto ME. “In x Out”: Reviewing the Group Bias through the Biological

Perspective. Temas Psicol. Published online 2017:1441-1502. doi:10.9788/tp2017.3-23en

99. 99.

Geng Y, Zhao W, Zhou F, et al. Oxytocin Enhancement of Emotional Empathy: Generalization

Across Cultures and Effects on Amygdala Activity. Front Neurosci. Published online July 31,

2018. doi:10.3389/fnins.2018.00512

100. 100.

Buffone AEK, Poulin MJ. Empathy, Target Distress, and Neurohormone Genes Interact to

Predict Aggression for Others–Even Without Provocation. Pers Soc Psychol Bull . Published

online September 10, 2014:1406-1422. doi:10.1177/0146167214549320

101. 101.

Grillon C, Krimsky M, Charney DR, Vytal K, Ernst M, Cornwell B. Oxytocin increases anxiety

to unpredictable threat. Mol Psychiatry. Published online November 13, 2012:958-960.

doi:10.1038/mp.2012.156

102. 102.

Jiang Y, Platt ML. Oxytocin and vasopressin flatten dominance hierarchy and enhance

behavioral synchrony in part via anterior cingulate cortex. Sci Rep. Published online May 29,

2018. doi:10.1038/s41598-018-25607-1

103. 103.

Everett JAC, Faber NS, Crockett M. Preferences and beliefs in ingroup favoritism. Front Behav

Neurosci. Published online February 13, 2015. doi:10.3389/fnbeh.2015.00015

104. 104.

Huang Y, Zhen S, Yu R. Distinct neural patterns underlying ingroup and outgroup conformity.

Proc Natl Acad Sci USA. Published online February 19, 2019:4758-4759.

doi:10.1073/pnas.1819421116

105. 105.

Feldblum JT, Manfredi S, Gilby IC, Pusey AE. The timing and causes of a unique chimpanzee

community fission preceding Gombe’s “Four-Year War.” Am J Phys Anthropol. Published

online March 22, 2018:730-744. doi:10.1002/ajpa.23462

106. 106.

Samuni L, Preis A, Mundry R, Deschner T, Crockford C, Wittig RM. Oxytocin reactivity during

intergroup conflict in wild chimpanzees. Proc Natl Acad Sci USA. Published online December

27, 2016:268-273. doi:10.1073/pnas.1616812114

107. 107.

Young LJ, Flanagan-Cato LM. Editorial comment: Oxytocin, vasopressin and social behavior.

Hormones and Behavior. Published online March 2012:227-229.

doi:10.1016/j.yhbeh.2012.02.019

108. 108.

Iyengar S, Massey DS. Scientific communication in a post-truth society. Proc Natl Acad Sci

USA. Published online November 26, 2018:7656-7661. doi:10.1073/pnas.1805868115

109. 109.

Bolsen T, Druckman JN, Cook FL. Citizens’, Scientists’, and Policy Advisors’ Beliefs about

Global Warming. The ANNALS of the American Academy of Political and Social Science .

Published online February 8, 2015:271-295. doi:10.1177/0002716214558393

110. 110.

Ferris C. Vasopressin/oxytocin and aggression. Novartis Found Symp. 2005;268:190-198;

discussion 198-200, 242-253. https://www.ncbi.nlm.nih.gov/pubmed/16206881

111. 111.

Kawada A, Nagasawa M, Murata A, et al. Vasopressin enhances human preemptive strike in

both males and females. Sci Rep. Published online July 4, 2019. doi:10.1038/s41598-019-

45953-y

112. 112.

Ericson J, Flacking R, Hellström-Westas L, Eriksson M. Changes in the prevalence of breast

feeding in preterm infants discharged from neonatal units: a register study over 10 years. BMJ

Open. Published online December 2016:e012900. doi:10.1136/bmjopen-2016-012900

113. 113.

Fletcher NK, Acevedo P, Herman JS, Paupério J, Alves PC, Searle JB. Glacial cycles drive rapid

divergence of cryptic field vole species. Ecol Evol. Published online November 23, 2019:14101-

14113. doi:10.1002/ece3.5846

114. 114.

Rikalainen K, Aspi J, Galarza JA, Koskela E, Mappes T. Maintenance of genetic diversity in

cyclic populations-a longitudinal analysis inMyodes glareolus. Ecology and Evolution .

Published online June 11, 2012:1491-1502. doi:10.1002/ece3.277

115. 115.

Franklin MT, Myers JH, Cory JS. Genetic Similarity of Island Populations of Tent Caterpillars

during Successive Outbreaks. López-Vaamonde C, ed. PLoS ONE. Published online May 23,

2014:e96679. doi:10.1371/journal.pone.0096679

116. 116.

Miraldo A, Li S, Borregaard MK, et al. An Anthropocene map of genetic diversity. Science.

Published online September 29, 2016:1532-1535. doi:10.1126/science.aaf4381

117. 117.

Smith BT, Seeholzer GF, Harvey MG, Cuervo AM, Brumfield RT. Correction: A latitudinal

phylogeographic diversity gradient in birds. PLoS Biol. Published online July 14,

2017:e1002610. doi:10.1371/journal.pbio.1002610

118. 118.

Manel S, Guerin P-E, Mouillot D, et al. Global determinants of freshwater and marine fish

genetic diversity. Nat Commun. Published online February 10, 2020. doi:10.1038/s41467-020-

14409-7

119. 119.

Millette KL, Fugère V, Debyser C, Greiner A, Chain FJJ, Gonzalez A. Worldwide impacts of

humans on animal genetic diversity. Published online January 23, 2019. doi:10.1101/527739

120. 120.

van Holstein L, Foley RA. Terrestrial habitats decouple the relationship between species and

subspecies diversification in mammals. Proc R Soc B. Published online March 18,

2020:20192702. doi:10.1098/rspb.2019.2702

121. 121.

Tackenberg MC, McMahon DG. Photoperiodic Programming of the SCN and Its Role in

Photoperiodic Output. Neural Plasticity. Published online 2018:1-9. doi:10.1155/2018/8217345

122. 122.

Coomans CP, Ramkisoensing A, Meijer JH. The suprachiasmatic nuclei as a seasonal clock.

Frontiers in Neuroendocrinology. Published online April 2015:29-42.

Cyclical Evolutionary Mechanism Hypothesis Proudly powered by WordPress

doi:10.1016/j.yfrne.2014.11.002

123. 123.

Wahl S, Engelhardt M, Schaupp P, Lappe C, Ivanov IV. The inner clock—Blue light sets the

human rhythm. J Biophotonics. Published online September 2, 2019.

doi:10.1002/jbio.201900102

124. 124.

Duffy JF, Czeisler CA. Effect of Light on Human Circadian Physiology. Sleep Medicine Clinics.

Published online June 2009:165-177. doi:10.1016/j.jsmc.2009.01.004