Evolution of Culture Capacity Human Evolution Theory of Natural Selection Theory formulated by...

Evolution of Culture Capacity

Human Evolution

Theory of Natural Selection

Theory formulated by Charles Darwin.

Changes in living organisms occur over time as a result of reproduction.

The most convincing scientific explanation of the variety and history of life on earth.


No two living things, even those of the same species, are alike.

Sources of variation:Mutation

Sexual reproduction

Genetic drift

The chemical structure of DNA consists of two long backbones made of alternating sugar and phosphate molecules.

There are two pools of genetic

variation, hidden and expressed.

Figure 03.23

This computer simulation demonstrates that genetic drift causes isolated

populations to become genetically different from one another.


Most creatures did not survive long enough to have offspring.

Creatures who won the struggle for survival passed traits that led to their success to their offspring.

Life in a nutshell: the cells of organisms are composed of a large number of very complicated chemicals

Stabilizing selection favors the intermediate phenotype out of a range of phenotypes. The extremes in variation are selected against. Example: Human infants weighing significantly less or more than 7.5 pounds have higher rates of infant mortality. Selection works against both extremes.

Directional Selection tends to favor phenotypes at one extreme of the range of variation. Insecticide resistance is an example. DDT was a widely used insecticide. After a few years of extensive use, DDT lost its effectiveness on insects. Resistance to DDT is a genetic trait that the presence of DDT in the environment made into a favored trait. Only those insects resistant to DDT survived, leading over time to populations largely resistant to DDT.

Disruptive Selection favors individuals at both extremes of variation: selection is against the middle of the curve. This causes a discontinuity of the variations, causing two or more morphs or distinct phenotypes. The African swallowtail butterfly (Papilo dardanus) produces two distinct morphs, both of which resemble brightly colored but distasteful butterflies of other species. Each morph gains protection from predation although it is in fact quite edible.

Types of

Natural

Selection

Selection Pressures can be observed in local micro-environments where severe conditions prevail

The same mechanisms are at work in developing new crops through artificial selection.

Common Examples of Selection In Action

Selection can carry a population far beyond the original range of variation.

Illustration of Artificial Selection for Oil Content in Corn.

Selection Against Oil content

Selection For Oil Content

HARDY-WEINBERG EQUILIBRIUM THEORY

A MATHEMATICAL MODEL OF AN IDEAL POPULATION IN WHICH GENE FREQUENCIES ARE.NOT INFLUENCED BY EVOLUTIONARY PROCESSES. THE MODEL.MAKES THE FOLLOWING ASSUMPTIONS: A LARGE (INFINITELY?) POPULATION. NO MUTATION NO MIGRATION NO SELECTI ON COMPLETELY RANDOM.MATINGS

EVOLUTION TERMINOLOGY

GENE POOL: THE TOTAL NUMBER OF ALLELES IN A POPULATION. THE GENE POOL REPRESENTS THE AVAILABLE GENETIC VARIATION.

BREEDING ISLOLATES: A POPULATION THAT IS ISOLATED, OR SEMI- ISOLOATED, FROM OTHER POPULATIONS FOR GEOGRAPHIC, BEHAVIORAL, OR OTHER.REASONS.

ENDOGAMY: MATING WITHINA SOCI.AL GROUP.

EXOGAMY: MATING OUTSIDE A SOCIAL GROUP.

Figure 04.02a

Gene flow among populations destroys differences between them.

Island 1 Island 2

Figure 04.02b

Island 1 Island 2Now suppose two populations of finches live on different islands, one wet and one dry, with no gene flow between the two islands

Figure 04.03

In the Galápagos, selection maintains three species of ground finches despite the fact that there is substantial gene flow among them


NEGATIVE ASSORTIVE MATING: INDIVIDUALS OF UNLIKE PHENOTYPE MATE MORE OFTEN THAN THOSE OF SIMILAR PHENOTYPES.

POSITIVE-ASSORTIVE MATING: INDIVIDUALS OF LIKE PHENOTYPE MATE MORE OFTEN THAN THOSE OF SIMILAR PHENOTYPES.

INBREEDING: THE SYSTEMATIC SELECTION OF MATES FROM CLOSE GENETIC RELATIVES.

CONSANGUINITY: THE DEGREE OF RELATION BETWEEN INDIVIDUALS.

Figure 04.10

Allopatric speciation occurs when a species is divided into two reproductively isolated populations that subsequently diverge. If the divergent populations regain contact, they cannot interbreed and two new species exist.

Types of Speciation

Parapatric speciation occurs when a species experiences different environments in different parts of its geographic range. Natural selection causes different populations of the species to diverge while adapting to these different surroundings, and eventually reproductive isolation is achieved.

Sympatric speciation occurs when selection strongly favors different adaptations to a similar environment within a single species.


FOUNDER EFFECT: THIS OCCURS WHEN A.VERY SMALL NUMBER OF INDIVIDUALS (AND THEREFORE A VERY SMALL GENE POOL) ARE THE ONLY INDIVIDUALS TO CONTRIBUTE GENES TO THE .FOLLOWING GENERATIONS.

An illustration of

sampling variation.

Anagenesis and CladogenesisThere are two types of change. These are depicted here as anagenesis and cladogenesis. The latter, of course, implies the process of speciation. The former relates to changes over time in a species.

There are three terms that you should know relative to evolution. These are: Divergent Evolution, Convergent Evolution, and Parallel Evolution. The keys to understanding the differences between these terms is to contrast ancestry, adaptations, and eventual forms. If you do this, you will find these terms easy to understand.

DIVERGENT EVOLUTION Evolution of DIFFERENT adaptive traits in forms that were once related but then diverged, developing along different lines. In terms of ancestry, adaptation and form: there is similar ancestry, different adaptations and resulting different forms.

CONVERGENT EVOLUTION Evolution of SIMILAR adaptive traits In terms of ancestry, adaptation and form - consider convergent evolution to reflect different ancestries, similar adaptations and resulting similar forms.

PARALLEL EVOLUTION

Evolution of similar adaptive traits in forms that were once related but then diverged, developing along similar lines.

In terms of ancestry, adaptation and form: there is similar ancestry, similar adaptations and resulting similar forms.

Debates on Evolution

Most debate about evolution is religious rather then scientific.Evolution challenges religious creation stories. In 1950, the Catholic Church declared evolution compatible with Christianity.

Common Ancestors

Humans, gorillas and chimpanzees evolved from common ancestors.

All animals are equally evolved in different ways and under different circumstances.

Human ancestors diverged from those of chimpanzees and gorillas 5 to 8 m.y.a.

Primates

For our purposes, Primates have the following features:Limbs and Locomotion

1. Retention of Five Digits (pentadactyly)2. Nails instead of claws on at least some digits. 3. Flexible hands and feet with considerable prehensility4. Retention of the Clavicle5. A tendency towards erect posture, especially in the upper body

• Teeth and Diet1. A generalized dental pattern2. A lack of specialization in diet

Senses, Brain, and Behavior1. A reduction of the snout2. An increased emphasis on vision3. Expansion and increased complexity of the brain4. A more efficient means of fetal nourishment, lengthening of the entire life-cycle,

especially of gestation and infancy. 5. Dependency on highly flexible learned behavior6. Adult males often associate with the group permanently

Suborder Prosimii

Grade One: Tree Shrews (primitive mammalian grade)

•Live in southeast Asia, India to Indonesia

•Have claws, not nails, on all digits

•Have grasping hands

•Probably resemble some of the earliest primates

Grade Two: Lemurs and Lorises

•Lemurs: Only on the island of Madagascar. Extinct elsewhere

•Lorises: Very similar to Lemurs, but are distributed over much of

Southern Africa

Summary of the Prosimians: 1. Have nails on at least one digit 2. Well developed vision, but not completely stereoscopic. 3. Prolonged life spans 4. Projecting nose 5. Well-developed sense of smell 6. Expressionless faces 6. Grooming dentition 7. Unelaborated social structure.

Grades of Primate Evolution

Suborder Anthropoidea

Grade Four: Monkeys

A. New world Monkeys: Ceboidea•Exclusively Arboreal•Southern Mexico, Central America, South America•Some have prehensile tails

B. Old world Monkeys: Cercopithecoidea•The most widely distributed of all primates other than humans•2.1.2.3 dental formula•All quadrapedal, mainly arboreal•No prehensile tails in adults

Grade Five: HominoidsA. Lesser Apes: Gibbons and SiamangsB. Great Apes: Orangutans, Gorillas, ChimpsC. Humans

Primate Social Behavior

Core of society is the bond between mothers and their offspring.

Play becomes central to the interaction of older primates with their age-mates.

Primates have displays of aggression and means of reconciliation.

Primate Social Behavior

Mother-Infant Relationship: The basic social unit in all primates.

Males may consort with females for mating, but they may or may not participate as members of a social unit. In most other animals infants are left behind in dens or nests. In Primates: 1. Infants cling to mothers while they move about. 2. The bond is often for life, and is reflected in adult grooming

behavior.

The role of the mother-infant attachment is not just one of social stability, it is absolutely essential for the proper development of primate infants.

What are some of the basic types of non-human primate social groups?

1. ONE MALE GROUPS

a. A single adult male, several adult females and their offspring. b. The most common primate mating structurec. Only one male actively breeds. d. Usually formed by a male or males joining a kin group of females. e. Females usually form the permanent nucleus of the group. f. Examples: Guenons, Orangs, Gorillas, pottos (some), spider monkeys (some), patas.

2. MULTIMALE GROUPSa. Several adult males, several adult females and their young. b. Several of the males reproduce. c. The presence of several males may lead to tension and to a dominance hierarchy. d. Examples: Lemurs(some), macaques, mangabeys, savanna baboons, vervets, chimpanzees.

3. FAMILY, or MONOGAMOUSa. A mated pair and their young. b. Usually arborealc. Minimal sexual dimorphismd. Frequently territorial; Adults do not tolerate other adults of the same sex. e. Not found among the great apes, and least common of breeding structures in non-human

primates. f. Examples: gibbons, indris, tarsiers, owl monkeys, titis, pottos, marmosets(some).

ASPECTS OF SOCIAL BEHAVIOR

Grooming: The manual cleaning of skin and fur. 1. Almost all primates groom one another2. Grooming occurs in other species but SOCIAL grooming is a

unique primate activity and plays an important role in the life of most primates.

3. Eases interaction between male/female and lower/higher ranks: “social lubricant”

4. The social cement for all primates: helps maintain social organization of the group.

5. Often reciprocal with roles interchanged; groomer becomes the groomee


Displays: Stereotyped behavior what serves to communicate emotional signals.

1. Animals often display when excited

2. They use displays

a. when outsiders are present

b. in reaction to another member of the group.


Dominance (dominance hierarchy): The physical domination of some members of a group by other members. 1. Measured by priority access to a desired

object such as food or a mate. 2. The dominant individual is given priority

in confrontations. 3. Dominant individuals compete more successfully in the group than others: net reproductive success.

Females first develop tool-using skills and become more adept than males.

Tool use is learned behavior and passed along by the social group.

Some groups of chimpanzees do some activities and others do not.

Primate Tool Use

Examples of Primate Tool Use

Use sticks to threaten others or defend themselves.

Use water to separate grains of wheat from sand.

Use twigs or blades of grass to fish termites from their mounds.

Early Human Ancestors

Few in number and geographically confined to Africa.

Did not depend heavily on tools, and left few material remains.

Spread from African origins to inhabit most of the globe.

Evolution of Humans

Humans have adapted to many different climates and ecosystems.

All humans are members of the biological family Hominidae.

Humans fall into two genera: Australopithecus and Homo.

http://www.handprint.com/cgi-bin/imagemap/my_map.map

•Expanded cranial capacity (relative to africanus). •Reduced postcanine tooth size. •The presence of a precision grip (determined from the hand bones present in OH 7), which provides the anatomical basis for tool-making.

Homo Habilis

Homo Habilis

Found in Africa between 2.5 and 1.8 million years ago.

Made sophisticated sets of tools as early as 2.3 million years ago.

Stone rings indicate that habilis probably built shelters for protection.

Homo erectus•An increase in brain size (erectus approximately 900 cc., sapiens approximately 1350 cc.).

•A reduction in postcanine dentition, and a correlated decrease in jaw size.

•Vertical shortening of the face.

•Shortening of armbones (especially the forearm) to come to a very humanlike limb proportions (postcranial proportions are very similar to tropically adapted modern humans).

•The development of a more barrel-shaped chest.

•The formation of an external nose.

•Reached modern human size in terms of height.

Homo erectus

Found in Africa, Asia, and Europe between 1.8 million and about 200,000 years ago.

Became increasingly dependent on culture to survive in the Ice Age.

Capable of controlling and using fire.

Lived by hunting, scavenging, and gathering.

NeandertalsAmud 1

•Flat zygomatic arch.

•The supraorbital torus projects at midline.

•Retreating chin.

•A long low brain case. .

•An occipital bun.

•A broad and projecting nose.

•Larger cranial capacity (but due to larger body size, Neanderthals are less encephalized than modern humans).

Neandertals

Members of a population of archaic Homo sapiens.

Lived between 130,000 and 35,000 years ago.

Pollen found in graves show bodies were buried with flowers, suggesting rituals and belief in the afterlife.

Homo sapiens sapiens

•A high, rounded cranium. •A steep forehead. •Large cranial capacity (1600 cc.). •A short face with rectangular orbitals. •A tall and narrow nasal opening. •A parabolic palate. •A prominent mental eminence.

Homo sapiens sapiens

Tools were more sophisticated and efficient than any prior species.

Left symbolic and artistic remains in form of cave paintings and Venus figures.

Turned to the domestication of plants and animals about 10,000 years ago.

Human Variation

Human traits change in frequency geographically.Blood type and skin color vary geographically.The sickle cell gene is common in areas that have a high incidence of malaria.

Evolution of Culture Capacity Human Evolution Theory of Natural Selection Theory formulated by...

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