Chapter 7: Problems of Parenting Aubrey Parlet Honors Seminar Fall 2006.

Chapter 7: Problems of Chapter 7: Problems of ParentingParenting

Aubrey ParletAubrey Parlet

Honors Seminar Fall 2006Honors Seminar Fall 2006

IntroductionIntroduction

How would you define “Offspring”?How would you define “Offspring”?

What are Offspring?What are Offspring?

1. They are a genetic 1. They are a genetic vehicle for their parents.vehicle for their parents.

2. They are the means 2. They are the means by which their parents’ by which their parents’ genes may get genes may get transported to transported to succeeding generations. succeeding generations.

If offspring are so important, do all If offspring are so important, do all life forms engage in parental care? life forms engage in parental care?

No.No. Example: Oysters release Example: Oysters release

their sperm and eggs into their sperm and eggs into the ocean to fend for the ocean to fend for themselves. For every themselves. For every oyster that survives, oyster that survives, thousands die.thousands die.

Also, by investing in Also, by investing in offspring, parents lose out offspring, parents lose out on resources that could be on resources that could be used on themselves.used on themselves.

Parents who protect their Parents who protect their young often risk their own young often risk their own survival.survival.

Example of the evolution of Example of the evolution of parental care: Mexican Batsparental care: Mexican Bats

After giving birth, the mother bats After giving birth, the mother bats leave densely populated caves to leave densely populated caves to forage for food.forage for food.

Upon returning to the cave, 83% Upon returning to the cave, 83% of mother bats find their own pup of mother bats find their own pup (among the thousands of baby (among the thousands of baby pups) and feed only their own pups) and feed only their own pup.pup.

This shows that the mother bats This shows that the mother bats have evolved mechanisms for have evolved mechanisms for detecting their own pup and these detecting their own pup and these mechanisms are designed to help mechanisms are designed to help her own genetic offspring, not the her own genetic offspring, not the offspring of the bat species as a offspring of the bat species as a whole.whole.

http://video.google.com/videosearch?q=mexican+bats&hl=en

Another example of the evolution of Another example of the evolution of parental care: Nesting Birds parental care: Nesting Birds

After the new chicks have After the new chicks have hatched, the mother birds hatched, the mother birds laboriously remove all laboriously remove all pieces of the now broken pieces of the now broken shell to locations far away.shell to locations far away.

The purpose of this is to The purpose of this is to make the nest look less make the nest look less attractive to predators. attractive to predators.

In this situation, the effort of In this situation, the effort of parental care is outweighed parental care is outweighed by the benefits of increased by the benefits of increased survival of chicks (through survival of chicks (through decreased likelihood of decreased likelihood of predators attacking).predators attacking).

Why is there parental love?Why is there parental love?

Despite the knowledge that mothers tend to Despite the knowledge that mothers tend to love their children, the phenomenon of love their children, the phenomenon of powerful love has continued to confuse powerful love has continued to confuse psychologists at a theoretical level. psychologists at a theoretical level.

From an evolutionary perspective, the reasons From an evolutionary perspective, the reasons for parental love seem clear: they are designed for parental love seem clear: they are designed to ensure the reproduction of one’s genes from to ensure the reproduction of one’s genes from one generation to the next. This leads us to one generation to the next. This leads us to our next question…our next question…

Why do mothers in so many species Why do mothers in so many species provide parental care so much more provide parental care so much more

than fathers do?than fathers do? One thing that should One thing that should

be considered is:be considered is: The Paternity The Paternity

Uncertainty HypothesisUncertainty Hypothesis

The Paternity Uncertainty The Paternity Uncertainty Hypothesis Hypothesis

1. Mothers are 100% sure that their offspring are genetically “theirs” and no 1. Mothers are 100% sure that their offspring are genetically “theirs” and no one else’s. one else’s.

2. Males cannot be this certain. From a male perspective, there can always be 2. Males cannot be this certain. From a male perspective, there can always be some probability that another male has fertilized the female’s egg.some probability that another male has fertilized the female’s egg.

3. Paternity uncertainty is strongest in species with internal female 3. Paternity uncertainty is strongest in species with internal female fertilization, and includes:fertilization, and includes:

-Humans-Humans -All primates-All primates -Insects-Insects -All mammals-All mammals 4. Males suffer tremendous costs by channeling their resources to other men’s 4. Males suffer tremendous costs by channeling their resources to other men’s

descendants. Therefore, if there is any uncertainty, it is in the interest of the descendants. Therefore, if there is any uncertainty, it is in the interest of the man not to invest in offspring that may or may not be his.man not to invest in offspring that may or may not be his.

5. If males cannot be counted on to invest in a female’s offspring, the female 5. If males cannot be counted on to invest in a female’s offspring, the female must provide the bulk of the care, leading in turn to loving the offspring more must provide the bulk of the care, leading in turn to loving the offspring more because more is invested.because more is invested.

The Paternity Uncertainty The Paternity Uncertainty HypothesisHypothesis

Do you think it’s true that if females must Do you think it’s true that if females must provide the bulk of the care (because males provide the bulk of the care (because males can’t be depended on), that this increase in can’t be depended on), that this increase in investment leads to more love of the investment leads to more love of the offspring? offspring?

Another Hypothesis: The Another Hypothesis: The Abandonability Hypothesis Abandonability Hypothesis

This cites the order in which eggs and This cites the order in which eggs and sperm are released as the determining sperm are released as the determining factor.factor.

After a male releases his sperm, he is After a male releases his sperm, he is free to leave whereas the female is left to free to leave whereas the female is left to give birth and decide whether or not to give birth and decide whether or not to invest in her offspring.invest in her offspring.

In species where the female contributes In species where the female contributes her egg before the male contributes his her egg before the male contributes his sperm, the roles would be reversed, sperm, the roles would be reversed, leaving the male in the position to either leaving the male in the position to either invest or not invest in his offspring.invest or not invest in his offspring.

From this it follows that female parental From this it follows that female parental care should be more prevalent in species care should be more prevalent in species with internal female fertilization whereas with internal female fertilization whereas male parental care should be more male parental care should be more prevalent in species with external prevalent in species with external fertilization.fertilization.

Abandonability Hypothesis Abandonability Hypothesis ContinuedContinued

This hypothesis does have This hypothesis does have some support:some support:

In a study of fish and In a study of fish and amphibians, those species amphibians, those species with internal female with internal female fertilization had 86% of fertilization had 86% of females providing the bulk females providing the bulk of parental care, whereas of parental care, whereas 70% of species with 70% of species with external fertilization had external fertilization had males providing the bulk of males providing the bulk of parental care.parental care.


There are two problems There are two problems with this hypothesis:with this hypothesis:

First, it is likely that First, it is likely that paternity uncertainty is paternity uncertainty is higher in species with higher in species with internal female fertilization internal female fertilization than in those with external than in those with external fertilization because males fertilization because males have fewer means of have fewer means of deciding which sperm deciding which sperm actually fertilize the actually fertilize the female’s eggs. With female’s eggs. With external fertilization, a male external fertilization, a male can tell which sperm can tell which sperm fertilized the eggs.fertilized the eggs.


Second, there are many Second, there are many species that release their species that release their gametes at the same time.gametes at the same time.

Taking such factors into Taking such factors into account, the abandonability account, the abandonability hypothesis by itself is not hypothesis by itself is not enough to explain the enough to explain the tendency of females to offer tendency of females to offer more parental care.more parental care.


What do you think of the Abandonability What do you think of the Abandonability Hypothesis? Does it make sense? Hypothesis? Does it make sense?

Another Hypothesis: The Mating Another Hypothesis: The Mating Opportunity Cost Hypothesis Opportunity Cost Hypothesis

Definition of “mating Definition of “mating opportunity costs”: opportunity costs”: Missed additional Missed additional mating encounters as a mating encounters as a direct result of effort direct result of effort devoted to offspring. devoted to offspring. This is suffered by This is suffered by males and females.males and females.

The Mating Opportunity Cost The Mating Opportunity Cost Hypothesis ContinuedHypothesis Continued

Mating opportunity costs are higher for males than for females Mating opportunity costs are higher for males than for females because the reproductive success of males is basically limited because the reproductive success of males is basically limited by the number of females that they can successfully by the number of females that they can successfully inseminate. (Women generally have a harder time of inseminate. (Women generally have a harder time of increasing reproductive output.)increasing reproductive output.)

According to this hypothesis, male parental care should be rare According to this hypothesis, male parental care should be rare when the opportunity costs of missed mating encounters for when the opportunity costs of missed mating encounters for males are high. (Conversely, when opportunity costs are low, males are high. (Conversely, when opportunity costs are low, conditions favor parental care.)conditions favor parental care.)

When considering humans, if there are more available men When considering humans, if there are more available men than women, men will be more likely to invest in parental care than women, men will be more likely to invest in parental care because they will have less success with a short-term mating because they will have less success with a short-term mating strategy. When there are more women available then men, the strategy. When there are more women available then men, the opposite will be true: men will invest less in offspring because opposite will be true: men will invest less in offspring because they have more opportunities to reproduce.they have more opportunities to reproduce.

Which Hypothesis is the “best”?Which Hypothesis is the “best”?

Of the three theories just discussed, which Of the three theories just discussed, which ones do you think best explain the reasons that ones do you think best explain the reasons that females invest more than males do?females invest more than males do?

The 3 theories discussed were:The 3 theories discussed were:

The Paternity Uncertainty Hypothesis The Paternity Uncertainty Hypothesis

The Abandonability Hypothesis The Abandonability Hypothesis

The Mating Opportunity Cost The Mating Opportunity Cost Hypothesis Hypothesis

An Evolutionary Perspective on An Evolutionary Perspective on Parental Care Parental Care

In general, selection will In general, selection will favor mechanisms of favor mechanisms of parental care that have the parental care that have the effect of increasing the effect of increasing the fitness of the parent and fitness of the parent and child.child.

Definition of Parental Definition of Parental Favoritism: Mechanisms Favoritism: Mechanisms of parental care will favor of parental care will favor some offspring over some offspring over others. others.

Parental FavoritismParental Favoritism

Do you think your parents engaged in parental Do you think your parents engaged in parental favoritism at any point while you were favoritism at any point while you were growing up? What about now?growing up? What about now?

Evolved mechanisms of parental Evolved mechanisms of parental care should be sensitive to care should be sensitive to

three contexts:three contexts: 1. Genetic relatedness of the 1. Genetic relatedness of the

offspring: Are the children really offspring: Are the children really my own?my own?

2. Ability of the offspring to 2. Ability of the offspring to convert parental care into fitness: convert parental care into fitness: Will a given unit of my investment Will a given unit of my investment make a difference to the survival make a difference to the survival and reproduction of my children?and reproduction of my children?

3. Alternative uses of the 3. Alternative uses of the resources that might be available resources that might be available to invest in offspring: Will a given to invest in offspring: Will a given unit of my investment be best unit of my investment be best spent investing in children or in spent investing in children or in other activities such as investing other activities such as investing in my sister’s children or in in my sister’s children or in additional mating opportunities?additional mating opportunities?

Genetic Relatedness to Offspring Genetic Relatedness to Offspring Example: Mr. GExample: Mr. G He was a man who He was a man who

discovered that his discovered that his daughter was not daughter was not biologically his. Despite a biologically his. Despite a close relationship with her close relationship with her prior to his discovery, he prior to his discovery, he cut off all ties with her. cut off all ties with her. This supports the idea that This supports the idea that a lack of paternity can be a a lack of paternity can be a huge factor in parental huge factor in parental investment.investment.

Genetic Relatedness to Offspring Genetic Relatedness to Offspring ContinuedContinued

Example: Stepmothers and Example: Stepmothers and FathersFathers

Only 53% of stepfathers and Only 53% of stepfathers and 25% of stepmothers claimed 25% of stepmothers claimed to have any “parental to have any “parental feelings” at all toward their feelings” at all toward their stepchildren. This indicates stepchildren. This indicates that parental investment is that parental investment is less likely (but not unheard-less likely (but not unheard-of) when one’s genes are of) when one’s genes are not directly affected.not directly affected.


Why do you think stepfathers are more likely Why do you think stepfathers are more likely to display parental feelings than stepmothers?to display parental feelings than stepmothers?


Webster’s DictionaryWebster’s Dictionary Definition of Definition of Stepmother:Stepmother: the wife of one’s father by a the wife of one’s father by a subsequent marriage; subsequent marriage; one one that fails to give proper that fails to give proper care or attentioncare or attention..

Example: Example: Cinderella,Cinderella, and and many other folktales across many other folktales across different cultures.different cultures.

How do men assess paternity?How do men assess paternity?

1. Information about his partner’s sexual fidelity 1. Information about his partner’s sexual fidelity (faithfulness)(faithfulness)

2. Perceptions of the child’s resemblance to him2. Perceptions of the child’s resemblance to him

Mothers will benefit if they are able to convince a man that a child Mothers will benefit if they are able to convince a man that a child resembles him because the man will invest more in the child.resembles him because the man will invest more in the child.

In one study, new mothers commented on the newborn’s resemblance to In one study, new mothers commented on the newborn’s resemblance to the man four times as often as she commented on the newborn’s the man four times as often as she commented on the newborn’s resemblance to herself (Daly & Wilson, 1982, p. 70).resemblance to herself (Daly & Wilson, 1982, p. 70).

In a second study, relatives of a couple with a newborn also agreed that a In a second study, relatives of a couple with a newborn also agreed that a newborn looked more like the father (66% supporting this scenario) than newborn looked more like the father (66% supporting this scenario) than the mother (only 34% supporting this scenario) (Daly & Wilson, 1982, p. the mother (only 34% supporting this scenario) (Daly & Wilson, 1982, p. 70).70).

These findings have also been replicated in a study of Mexicans residing in These findings have also been replicated in a study of Mexicans residing in the Yucatan (Regalski & Gaulin, 1993).the Yucatan (Regalski & Gaulin, 1993).

How do men assess paternity?How do men assess paternity?

Basically, it is a cross-cultural Basically, it is a cross-cultural phenomenon that mothers and phenomenon that mothers and their kin attempt to influence the their kin attempt to influence the putative father’s perception of his putative father’s perception of his paternity to encourage his paternity to encourage his parental investment in the child.parental investment in the child.

Men’s perceptions of their Men’s perceptions of their offspring’s resemblance to offspring’s resemblance to themselves may also affect things themselves may also affect things such as family violence.such as family violence.

In one study, men who thought In one study, men who thought their children looked like them their children looked like them reported better relationships with reported better relationships with their children, whereas men who their children, whereas men who thought their children did not look thought their children did not look like them were more likely to like them were more likely to inflict physical injuries on their inflict physical injuries on their partners (Burch & Gallup, 2000).partners (Burch & Gallup, 2000).

Parents’ Investment in ChildrenParents’ Investment in Children

Example study done by Anderson, Kaplan, & Lancaster Example study done by Anderson, Kaplan, & Lancaster (1999):(1999):

Hypothesis one: men will allocate more resources to their genetic Hypothesis one: men will allocate more resources to their genetic children than to their stepchildren.children than to their stepchildren.

Hypothesis two: men who are uncertain about whether children are Hypothesis two: men who are uncertain about whether children are genetically their own will invest less than men who are certain the genetically their own will invest less than men who are certain the children are their own.children are their own.

Hypothesis three: men will invest more in children when the Hypothesis three: men will invest more in children when the child’s mother is their current mate than they will in children from child’s mother is their current mate than they will in children from former mates.former mates.

They tested the amount of money a child received for college They tested the amount of money a child received for college education from their fathers in Albuquerque, New Mexico, and the education from their fathers in Albuquerque, New Mexico, and the results dramatically supported all three of their hypotheses.results dramatically supported all three of their hypotheses.


Similar effects were Similar effects were also demonstrated in also demonstrated in another study done on another study done on Xhosa high-school Xhosa high-school students living in Cape students living in Cape Town, South Africa, Town, South Africa, indicating that the indicating that the phenomenon may also phenomenon may also be cross-cultural.be cross-cultural.


Another example: Another example: Evolutionary Evolutionary anthropologist Frank anthropologist Frank Marlow found that Marlow found that among the Hadza of among the Hadza of Tanzania, stepfathers Tanzania, stepfathers invest less than genetic invest less than genetic fathers do. In his study, fathers do. In his study, not a single stepfather not a single stepfather engaged in direct play engaged in direct play with his stepchild.with his stepchild.

Genetic RelatednessGenetic Relatedness

To sum up, genetic relatedness to a child To sum up, genetic relatedness to a child is a good predictor of a male’s is a good predictor of a male’s investment in offspring. The more investment in offspring. The more certain the relatedness, the more the certain the relatedness, the more the investment will be.investment will be.

In your families, who provides the In your families, who provides the majority of the investment in you? majority of the investment in you? Mother? Father? Or both?Mother? Father? Or both?

Child Abuse and Other Risks of Not Child Abuse and Other Risks of Not Living with Both ParentsLiving with Both Parents

Parental care should be Parental care should be viewed as a continuum.viewed as a continuum.

On one end there is On one end there is extreme self-sacrifice extreme self-sacrifice (even risking one’s own (even risking one’s own life) for the benefit of life) for the benefit of the offspringthe offspring

On the other end, there On the other end, there are events that inflict are events that inflict costs on the offspring, costs on the offspring, such as child abuse.such as child abuse.


Infanticide is perhaps Infanticide is perhaps the most extreme: it is the most extreme: it is the killing of an infant. the killing of an infant. It can be predicted by It can be predicted by genetic relatedness. The genetic relatedness. The more related one is to an more related one is to an infant, the less likely infant, the less likely they will be to harm the they will be to harm the infant or kill the infant.infant or kill the infant.

Example: study done by Daly & Example: study done by Daly & Wilson (1985)Wilson (1985)

They surveyed households They surveyed households and found that children and found that children living with one genetic living with one genetic parent and one stepparent parent and one stepparent are are forty timesforty times more likely more likely to be physically abused than to be physically abused than children living with both children living with both genetic parents. (Poverty genetic parents. (Poverty and socioeconomic status and socioeconomic status were controlled for).were controlled for).

They concluded that They concluded that stepparent-hood is the single stepparent-hood is the single most powerful risk factor most powerful risk factor for child abuse that has thus for child abuse that has thus far been identified.far been identified.

Child Homicide as a Function of Child Homicide as a Function of Genetic Relatedness to OffspringGenetic Relatedness to Offspring

Example: Daly & Wilson Example: Daly & Wilson (1996)(1996)

They found that a child is more They found that a child is more likely to be killed by a likely to be killed by a stepparent than a natural parent stepparent than a natural parent at all ages.at all ages.

The age at which most children The age at which most children are killed by a stepparent is are killed by a stepparent is between 0-2 years old.between 0-2 years old.

This data has not received This data has not received support as a cross-culture support as a cross-culture phenomenon; however it has phenomenon; however it has been shown to be very been shown to be very prominent in Canada, where the prominent in Canada, where the data was gathered.data was gathered.

Another Example: Another Example: Daly & Wilson (1988)Daly & Wilson (1988)

In a survey it was found that In a survey it was found that adultery, presumably resulting adultery, presumably resulting in some uncertainty of in some uncertainty of paternity, was mentioned as paternity, was mentioned as grounds for killing a child in grounds for killing a child in fifteen of the thirty-nine fifteen of the thirty-nine societies in which infanticide societies in which infanticide was mentioned.was mentioned.

Among the Tikopia people of Among the Tikopia people of Oceania in Venezuela, men Oceania in Venezuela, men who married women who who married women who already had had children by already had had children by another man reportedly another man reportedly requested that they be killed requested that they be killed as a condition of the marriage.as a condition of the marriage.


In summary, stepparent relationships to In summary, stepparent relationships to children are the single greatest risk factors that children are the single greatest risk factors that have been identified thus far as leading to have been identified thus far as leading to child abuse and child homicide.child abuse and child homicide.

What do you think? Do you think stepparents What do you think? Do you think stepparents are the biggest risk factor in abuse?are the biggest risk factor in abuse?

Offspring’s Ability to Convert Parental Offspring’s Ability to Convert Parental Care into Reproductive SuccessCare into Reproductive Success

After considering genetic After considering genetic relatedness, the next critical relatedness, the next critical factor in predicting parental factor in predicting parental care is the ability of the care is the ability of the child to use that care.child to use that care.

It does not necessarily It does not necessarily follow that a parent would follow that a parent would invest more in a healthy invest more in a healthy child, nor does it follow that child, nor does it follow that they would invest more in they would invest more in an ill child. The key to an ill child. The key to remember is this…remember is this…

Offspring’s Ability to Convert Parental Offspring’s Ability to Convert Parental Care into Reproductive SuccessCare into Reproductive Success

A parent will be more likely to invest in a A parent will be more likely to invest in a child if that child has the ability to convert a child if that child has the ability to convert a given unit of parental care into fitness (be given unit of parental care into fitness (be benefited by the parental care).benefited by the parental care).

This is an unconscious process when a parent This is an unconscious process when a parent is deciding where to invest.is deciding where to invest.

Example: Geary (2000)Example: Geary (2000) He summarized a large body of He summarized a large body of

evidence that suggested that evidence that suggested that parental (and paternal) investment parental (and paternal) investment in children makes a notable in children makes a notable difference to the children’s physical difference to the children’s physical and social well-being.and social well-being.

He also noted that the more He also noted that the more resources parents have, as indicated resources parents have, as indicated by socioeconomic status, the lower by socioeconomic status, the lower the death rates of their children.the death rates of their children.

Furthermore, he noted that an Furthermore, he noted that an increased amount of time spent increased amount of time spent playing with a child is positively playing with a child is positively correlated with academic skills, correlated with academic skills, social skills, and subsequent social skills, and subsequent socioeconomic status. Paternal socioeconomic status. Paternal investment seems to carry these investment seems to carry these findings to even greater heights. findings to even greater heights.

Parental Neglect and Abuse of Children Parental Neglect and Abuse of Children with Congenital Abnormalitieswith Congenital Abnormalities

Children with a congenital disease such as cleft palate Children with a congenital disease such as cleft palate or Down syndrome are more likely to either be or Down syndrome are more likely to either be partially or completely abandoned by their parents.partially or completely abandoned by their parents.

Many children with a congenital disease are Many children with a congenital disease are institutionalized, and of those that are, roughly institutionalized, and of those that are, roughly 12% 12% are never visited by their parents. Also, 22% are are never visited by their parents. Also, 22% are only visited once per yearonly visited once per year. Those who are not . Those who are not institutionalized have higher incidences of abuse and institutionalized have higher incidences of abuse and neglect.neglect.

In summary, parents invest less in children with In summary, parents invest less in children with abnormalities.abnormalities.

Parental Neglect and Abuse of Children Parental Neglect and Abuse of Children with Congenital Abnormalitieswith Congenital Abnormalities

Do you think that it is true that parents invest Do you think that it is true that parents invest less in children with abnormalities? What less in children with abnormalities? What about monetary investment?about monetary investment?

Maternal Care Based on the Health Maternal Care Based on the Health of the Childof the Child

Example: Study by Example: Study by Janet Mann (1992)Janet Mann (1992)

Studied twins in which Studied twins in which one was healthier than one was healthier than the other. He observed the other. He observed the mother’s behavior the mother’s behavior towards each twin in a towards each twin in a variety of settings.variety of settings.

Example: Study by Janet Mann Example: Study by Janet Mann (1992)(1992)

He found that by 8 months old, all He found that by 8 months old, all mothers directed more positive mothers directed more positive maternal behaviors to the infant maternal behaviors to the infant that was healthier.that was healthier.

His findings led to the Healthy His findings led to the Healthy Baby Hypothesis: the health Baby Hypothesis: the health status of the child would affect status of the child would affect the degree of positive maternal the degree of positive maternal behavior (such as kissing, behavior (such as kissing, hugging, soothing, etc.)hugging, soothing, etc.)

In summary, mothers direct In summary, mothers direct greater maternal investment greater maternal investment toward infants who are of higher toward infants who are of higher reproductive value (those that are reproductive value (those that are healthier).healthier).

Age of the ChildAge of the Child

Example: Daly & Wilson Example: Daly & Wilson (1988)(1988)

Predicted that the younger Predicted that the younger the child, the higher the the child, the higher the likelihood that the parents likelihood that the parents would kill it, but this age-would kill it, but this age-dependent pattern of child dependent pattern of child homicide should not occur homicide should not occur when the killer is a non-when the killer is a non-relative because non-relative because non-relatives do not have the relatives do not have the same stake or interest in the same stake or interest in the child’s reproductive value.child’s reproductive value.


They discovered two things: They discovered two things: First, they found that the First, they found that the

risk of homicide by a risk of homicide by a natural parent decreases as a natural parent decreases as a child’s age increases. child’s age increases.

Secondly, they found that Secondly, they found that the risk that a child will be the risk that a child will be killed by a non-relative killed by a non-relative increases as age increases.increases as age increases.


In summary, it appears to be the increasing In summary, it appears to be the increasing reproductive value of children as they age that reproductive value of children as they age that accounts for the fact that genetic parents kill older accounts for the fact that genetic parents kill older children less often.children less often.

From their study it can be inferred that selection has From their study it can be inferred that selection has favored psychological mechanisms in parents favored psychological mechanisms in parents sensitive to the reproductive value of their children.sensitive to the reproductive value of their children.

My question: What about children who are gay or My question: What about children who are gay or lesbian or who don’t want to reproduce? Do parents lesbian or who don’t want to reproduce? Do parents stop investing in them because they have diminished stop investing in them because they have diminished reproductive value? What do you think?reproductive value? What do you think?

Investment in Sons versus Daughters: Investment in Sons versus Daughters: The Trivers-Willard HypothesisThe Trivers-Willard Hypothesis

The Trivers-Willard Hypothesis: the idea that parents The Trivers-Willard Hypothesis: the idea that parents will produce more sons and invest more in sons when will produce more sons and invest more in sons when they are in good condition and hence have a chance of they are in good condition and hence have a chance of producing a son who will be highly successful in the producing a son who will be highly successful in the mating game. If the parents are in poor condition and mating game. If the parents are in poor condition and have few resources to invest, then they should invest have few resources to invest, then they should invest more in daughters.more in daughters.

Tests of this hypothesis in humans have proved Tests of this hypothesis in humans have proved inconclusive. More detailed studies are needed to inconclusive. More detailed studies are needed to determine the conditions under which a son or daughter determine the conditions under which a son or daughter is better able to utilize units of parental investment.is better able to utilize units of parental investment.

Alternative Uses of Resources Alternative Uses of Resources Available for Investment in ChildrenAvailable for Investment in Children

The Principle of Finite The Principle of Finite Effort: As applied to Effort: As applied to parenting, this means that parenting, this means that the effort expended toward the effort expended toward caring for a child cannot be caring for a child cannot be allocated toward other allocated toward other adaptive problems such as adaptive problems such as personal survival, attracting personal survival, attracting additional mates, or perhaps additional mates, or perhaps investing in other kin.investing in other kin.

The Principle of Finite Effort:The Principle of Finite Effort: From a woman’s perspective, From a woman’s perspective,

two contexts that might affect two contexts that might affect these decisions are age and these decisions are age and marital status.marital status.

From a man’s perspective one From a man’s perspective one context that may affect context that may affect parenting effort is his parenting effort is his potential sexual access to potential sexual access to women.women.

Is marital status not an issue Is marital status not an issue for a man? The book didn’t for a man? The book didn’t list this for males…list this for males…

Women’s Age and InfanticideWomen’s Age and Infanticide As opportunities for As opportunities for

reproduction diminish, reproduction diminish, postponing childbearing postponing childbearing and rearing would be and rearing would be reproductively costly.reproductively costly.

From here it is expected From here it is expected that natural selection would that natural selection would favor a decision rule that favor a decision rule that causes older women to causes older women to invest immediately in invest immediately in children rather than children rather than postponing doing so. postponing doing so. (Whereas younger women (Whereas younger women may postpone investment may postpone investment in children.)in children.)

Example: Study by Daly and Example: Study by Daly and Wilson (1988Wilson (1988))

Hypothesized that younger woman should be more Hypothesized that younger woman should be more inclined than older women to commit infanticide.inclined than older women to commit infanticide.

Their hypothesis was strongly supported by data Their hypothesis was strongly supported by data gathered from the Ayoreo Indians. They found that gathered from the Ayoreo Indians. They found that the proportion of births leading to infanticide is the proportion of births leading to infanticide is highest among the youngest women and lowest highest among the youngest women and lowest among the oldest age group of women.among the oldest age group of women.

They gathered more data from Canadian women and They gathered more data from Canadian women and found the same to be true.found the same to be true.

Example: Study by Daly and Example: Study by Daly and Wilson (1988Wilson (1988))

Overall they concluded Overall they concluded from their research that from their research that infanticide is highest among infanticide is highest among younger women, who have younger women, who have the most opportunities for the most opportunities for future reproduction, and future reproduction, and lowest among older women, lowest among older women, who have fewer who have fewer opportunities for opportunities for reproduction.reproduction.

Can you think of other Can you think of other reasons besides age that reasons besides age that might be a factor in might be a factor in infanticide rates?infanticide rates?

Women’s Marital Status and Women’s Marital Status and InfanticideInfanticide

Example: Daly and Wilson Example: Daly and Wilson (1988)(1988)

They proposed that a They proposed that a woman’s marital status will woman’s marital status will affect the likelihood that she affect the likelihood that she will commit infanticide.will commit infanticide.

In six cultures it was In six cultures it was reported that an infant reported that an infant should be killed if there is should be killed if there is no man claiming to be the no man claiming to be the infant’s father.infant’s father.

Example: Daly and Wilson (1988)Example: Daly and Wilson (1988)

In 14 cultures, a woman’s In 14 cultures, a woman’s unwed status was declared a unwed status was declared a compelling reason for compelling reason for infanticide.infanticide.

In Canada between 1977 In Canada between 1977 and 1983, of the 12% of and 1983, of the 12% of births attributable to single births attributable to single mothers, these same births mothers, these same births accounted for half of the accounted for half of the reported or discovered cases reported or discovered cases of infanticide.of infanticide.

Example: Daly and Wilson (1988)Example: Daly and Wilson (1988)

Furthering their Furthering their research, they research, they concluded that both age concluded that both age and marital status are and marital status are positively correlated positively correlated with rates of infanticide.with rates of infanticide.

In summary, at every In summary, at every age bracket, unwed age bracket, unwed mothers are more likely mothers are more likely to commit infanticide.to commit infanticide.

Parental Effort versus Mating EffortParental Effort versus Mating Effort

Recall the two reasons that men and women have Recall the two reasons that men and women have evolved different decision rules about the tradeoffs evolved different decision rules about the tradeoffs between parenting and mating:between parenting and mating:

1. Men benefit more than women by gaining sexual 1. Men benefit more than women by gaining sexual access to additional mates (additional children to pass access to additional mates (additional children to pass on genes).on genes).

2. Paternity is generally less than 100% certain. A 2. Paternity is generally less than 100% certain. A man may or may not be supporting his genes being man may or may not be supporting his genes being passed down, whereas a woman is certain that she is passed down, whereas a woman is certain that she is supporting her genes being passed down.supporting her genes being passed down.


In all cultures studied thus far, women invest In all cultures studied thus far, women invest more in parenting than men.more in parenting than men.

Example: The Aka Pygmies of Central Africa Example: The Aka Pygmies of Central Africa are said to have “mothering men” because the are said to have “mothering men” because the men provide such extensive care to their men provide such extensive care to their infants (the men hold their infants more than infants (the men hold their infants more than men in any other culture), yet when analyzed, men in any other culture), yet when analyzed, the women still provide the majority of the the women still provide the majority of the investment.investment.


90% of single parents are 90% of single parents are women. This indicates the women. This indicates the preference among both preference among both sexes for the woman to be sexes for the woman to be the predominant care giver.the predominant care giver.

Do you think this really Do you think this really indicates a “preference”, or indicates a “preference”, or is it more of an attitude of is it more of an attitude of “it’s the woman’s “it’s the woman’s responsibility to care for the responsibility to care for the child”? It is a “preference” child”? It is a “preference” held by men, or by women?held by men, or by women?


Example Study: Hess, 1975Example Study: Hess, 1975 Studied pupil dilation of Studied pupil dilation of

men and women when men and women when shown slide pictures of shown slide pictures of infants.infants.

Women’s pupils dilated Women’s pupils dilated 17% whereas men’s pupils 17% whereas men’s pupils did not dilate at all, did not dilate at all, suggesting that women were suggesting that women were more interested and more interested and attracted to the pictures than attracted to the pictures than the men were.the men were.


Women can identify their Women can identify their newborn child within 6 newborn child within 6 hours merely by smell, hours merely by smell, whereas fathers cannot.whereas fathers cannot.

Women can more easily Women can more easily detect the emotions that detect the emotions that their infants are displaying.their infants are displaying.

Overall, women appear to Overall, women appear to have a host of parental have a host of parental mechanisms that are weak mechanisms that are weak or absent in men. or absent in men.


Presumably, then, men are using the effort not allocated Presumably, then, men are using the effort not allocated toward parenting for other adaptive problems, such as mating.toward parenting for other adaptive problems, such as mating.

In a study of the Aka Pygmies of Central Africa (Hewlett, In a study of the Aka Pygmies of Central Africa (Hewlett, 1991), low-status men appear to compensate for their low 1991), low-status men appear to compensate for their low status by increasing the effort they allocate to parenting, status by increasing the effort they allocate to parenting, whereas high-status men appear to be channeling extra effort whereas high-status men appear to be channeling extra effort into attracting additional mates.into attracting additional mates.

Even when men devote effort to parenting, it may be used as a Even when men devote effort to parenting, it may be used as a mating tactic rather than as a means to aid the viability of the mating tactic rather than as a means to aid the viability of the child (as shown in a study done by Barbara Smuts and David child (as shown in a study done by Barbara Smuts and David Gubernick, 1992). They found that a man may put effort into Gubernick, 1992). They found that a man may put effort into a child in order to attract that child’s mother.a child in order to attract that child’s mother.

The Theory of Parent-Offspring The Theory of Parent-Offspring ConflictConflict

Parents and children are Parents and children are related by 50%, but also related by 50%, but also differ by 50%. Since differ by 50%. Since they are only 50% they are only 50% related, sometimes they related, sometimes they will disagree. For this will disagree. For this reason, children will reason, children will often want things that often want things that their parents don’t want their parents don’t want to give them.to give them.


From a mother’s point of view, From a mother’s point of view, each child is equally beneficial to each child is equally beneficial to her gene’s reproductive success her gene’s reproductive success (assuming equal health (assuming equal health characteristics). However, from a characteristics). However, from a child’s point of view, they are child’s point of view, they are much more important than their much more important than their sibling because they want to pass sibling because they want to pass down their own genes and don’t down their own genes and don’t care as much about the genes of care as much about the genes of their siblings. This leads to their siblings. This leads to conflict as noted by Daly and conflict as noted by Daly and Wilson (1988) because whereas a Wilson (1988) because whereas a mother may want to divide assets mother may want to divide assets evenly, each child she has will evenly, each child she has will inevitably want more than their inevitably want more than their “fair share” (one half) of the “fair share” (one half) of the resources.resources.


Have your parents ever divided things Have your parents ever divided things “unfairly” between you and your siblings in “unfairly” between you and your siblings in your opinion? Do you think it is just your your opinion? Do you think it is just your point of view that things were unfair, or do point of view that things were unfair, or do you think that they were you think that they were actuallyactually unfair? unfair?


In summary, Trivers’s theory of In summary, Trivers’s theory of Parent-Offspring Conflict Parent-Offspring Conflict predicts that each child will predicts that each child will generally desire a larger portion generally desire a larger portion of the parent’s resources than of the parent’s resources than the parents want to give. This the parents want to give. This holds true even in cases where a holds true even in cases where a mother has only one offspring.mother has only one offspring.

From this theory, it follows that From this theory, it follows that selection will fashion selection will fashion adaptations in children to adaptations in children to manipulate parents to tilt manipulate parents to tilt resource allocation toward their resource allocation toward their own optimum.own optimum.


This theory leads to three hypotheses:This theory leads to three hypotheses: Parents and children will have conflicting ideas Parents and children will have conflicting ideas

about when a child should be weaned. (The about when a child should be weaned. (The parents in favor of an earlier time, the children in parents in favor of an earlier time, the children in favor of a later time.)favor of a later time.)

Parents will teach their children to value their Parents will teach their children to value their siblings more than children are naturally inclined siblings more than children are naturally inclined to.to.

Parents will tend to punish conflict between Parents will tend to punish conflict between siblings and reward cooperation.siblings and reward cooperation.

Mother-Offspring Conflict in UteroMother-Offspring Conflict in Utero

The biggest conflict is the possibility of abortion.The biggest conflict is the possibility of abortion. To overcome this possibility, an adaptation of fetuses To overcome this possibility, an adaptation of fetuses

is to product a human chorionic gonadotropin (hCG), is to product a human chorionic gonadotropin (hCG), which is a hormone the fetus secretes into the mother’s which is a hormone the fetus secretes into the mother’s bloodstream. It prevents the mother from having bloodstream. It prevents the mother from having menstrual periods and thus helps to prevent the baby’s menstrual periods and thus helps to prevent the baby’s being aborted.being aborted.


Another conflict is food Another conflict is food supply to the fetus.supply to the fetus.

When a fetus perceives that When a fetus perceives that it needs more nutrition, it it needs more nutrition, it releases a substance into the releases a substance into the mother’s bloodstream that mother’s bloodstream that causes her arteries to causes her arteries to constrict. This raises the constrict. This raises the mother’s blood pressure and mother’s blood pressure and therefore delivers more therefore delivers more blood (and hence nutrition) blood (and hence nutrition) to the fetus (this can damage to the fetus (this can damage the mother’s tissues). the mother’s tissues). Clearly the adaptation has Clearly the adaptation has evolved to benefit the fetus, evolved to benefit the fetus, even at the expense of the even at the expense of the mother.mother.


Both of these conflicts support Trivers’s Theory of Both of these conflicts support Trivers’s Theory of Parent-Offspring Conflict because they all lead to Parent-Offspring Conflict because they all lead to the conclusion that children will want more than the conclusion that children will want more than their parents are willing to give at times, and will their parents are willing to give at times, and will manipulate their parents into getting what they manipulate their parents into getting what they want.want.

What are some ways that children manipulate What are some ways that children manipulate their parents? What did you do as children? their parents? What did you do as children? What did your siblings do?What did your siblings do?

The Oedipal Complex RevisitedThe Oedipal Complex Revisited

There are two central There are two central components to Freud’s components to Freud’s (1900/1953) Oedipus (1900/1953) Oedipus Complex:Complex: First, the son, between the First, the son, between the

ages of 2 and 5, is ages of 2 and 5, is hypothesized to develop a hypothesized to develop a sexual attraction toward his sexual attraction toward his mother. The son’s sexual mother. The son’s sexual attraction places him in attraction places him in conflict with his father.conflict with his father.

Second, a son will have an Second, a son will have an unconscious desire to kill unconscious desire to kill his father because they his father because they have become sexual have become sexual competitors for the mother.competitors for the mother.


The prediction that The prediction that follows these two follows these two components is:components is:

If the theory is correct, If the theory is correct, there will be more same-there will be more same-sex conflict and sex conflict and antagonism between antagonism between parent and child than parent and child than opposite-sex antagonism, opposite-sex antagonism, especially during the especially during the Oedipal stage, between Oedipal stage, between the ages of two and five.the ages of two and five.

The Oedipal Complex RevisitedThe Oedipal Complex Revisited This theory is different from Trivers’s Parent-Offspring This theory is different from Trivers’s Parent-Offspring

Conflict theory because Trivers’s theory has nothing to Conflict theory because Trivers’s theory has nothing to do with gender.do with gender.

This theory is different from Darwin’s theory of sexual This theory is different from Darwin’s theory of sexual selection because while Darwin’s theory does say that selection because while Darwin’s theory does say that members of one sex will become rivals over sexual members of one sex will become rivals over sexual access to members of the opposite sex, it does not access to members of the opposite sex, it does not suggest that the mother will become the target of this suggest that the mother will become the target of this sexual rivalry. In fact, since we know that men prefer sexual rivalry. In fact, since we know that men prefer younger women, we would predict that sons would not younger women, we would predict that sons would not have an attraction to their older mothers.have an attraction to their older mothers.

Did you or your siblings ever have an Oedipal complex Did you or your siblings ever have an Oedipal complex that you remember or that you’ve been told about?that you remember or that you’ve been told about?


Due to “inbreeding Due to “inbreeding complications” such as complications” such as a lowered intelligence a lowered intelligence level, it can be level, it can be suggested that suggested that selection would selection would operate against sexual operate against sexual attraction between a attraction between a son and his mother.son and his mother.

Example study: Daly and Wilson Example study: Daly and Wilson (1990)(1990)

Studied the rates of same-sex homicide Studied the rates of same-sex homicide between parents and their offspring between parents and their offspring and found no correlation between and found no correlation between same-sex homicides and the oedipal same-sex homicides and the oedipal stage among parents and offspring, stage among parents and offspring, therefore lending no support to the therefore lending no support to the Oedipus Complex theory.Oedipus Complex theory.

However, as age increased toward However, as age increased toward puberty and adulthood, a same-sex puberty and adulthood, a same-sex pattern did emerge, and was mostly pattern did emerge, and was mostly between fathers and sons and rarely between fathers and sons and rarely between females. This data supports between females. This data supports Trivers’s theory of Parent-Offspring Trivers’s theory of Parent-Offspring Conflict more than it supports the Conflict more than it supports the Freudian theory of the Oedipus Freudian theory of the Oedipus Complex.Complex.

ConclusionConclusion

In conclusion, the preliminary data are In conclusion, the preliminary data are inconclusive and suggest that parent-offspring inconclusive and suggest that parent-offspring conflict will be an important domain for future conflict will be an important domain for future empirical studies in evolutionary psychology.empirical studies in evolutionary psychology.

HAVE A GREAT HAVE A GREAT FALL BREAK FALL BREAK

EVERYONE! EVERYONE!

Chapter 7: Problems of Parenting Aubrey Parlet Honors Seminar Fall 2006.

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Transcript of Chapter 7: Problems of Parenting Aubrey Parlet Honors Seminar Fall 2006.