View
222
Download
4
Category
Preview:
Citation preview
Two Approaches to the Evolution of Kinship
1. The Study of Our Primate Relatives.2. Evolutionary Psychology
Our Primate RelativesProsimians (Lemurs, Lorises, Galagos)Monkeys (Baboons, Tamarins)Apes
Gibbons and Siamangs (Lesser Apes)OrangutansGorillasChimpanzees
Common ChimpsBonobo Chimps
Prosimians
Lemur – multimale and multifemale groups
Galago – solitary and promiscuous
Loris- monogamous when associate with another animal
Primate Characteristics
Binocular, stereoscopic vision. Opposable thumb/toe Grasping hand/foot Flat nails rather than claws Prolongation of gestation Prolongation of infancy and childhood Enlarged and elaborated brain
Monkeys: Old World and New World
Baboon – Polygynous – one male controls multiple females who mate exclusively with him
Tamarin – Polyandrous – one female mates with multiple males who all stay and care for young.
Gibbons and Siamangs
Monogamous for life – territorial and drive our same sex offspring at adolescence.
Gorilla98% Identical to Humans Genetically
Male-Centered groups – polygynous – with dominant males having mating priority in groups andcompetition between males for mating.
Chimpanzees98.6% Identical Genetically to Humans
www.slwaldron.com/BonoboGallery/
Bonobo
Common Chimp
Chimps98.6% Identical to Humans Genetically Common Chimps
Male-centered groups
Females leave natal group at adolescence to join another group
Males stay in the same group for life
Bonobos
Female-centered groups
Males leave natal group at adolescence to join another group
Females stay in the same group for life
WHY THE DIFFERENCE?????
Chimp/Bonobo Differences HYPOTHESIS One uniform species of chimp lived in the same regions as gorillas, who
dominated resources located on land, relegating chimps to the resources in the trees.
Drought separated the region into two areas.
Gorillas became extinct in one area; both gorillas and chimps survived in the other area.
In the area where both chimps and gorillas survived, the patterns of ground and tree resource use continued and chimps retained male dominance as a major organizing principle. Feeding for chimps took place in the trees, making alliances between females difficult and reinforcing male dominance.
Without competition for resources on the ground, chimps were free to utilize these resources and spent great amounts of time on the ground. This allowed females to unite against males, making them equal to or dominant over them.
Bonobos time on the ground meant that they spent more time bipedally.
Sociobiology Evolutionary Psychology
Biologists
Primatologists
Ethologists
Anthropologists
Psychologists
Linguists
Lots of Controversy
Fear of Social Darwinism
Arguments about human free will
Arguments about whether humans have instinctive (genetically programmed behavioral tendencies)
First attempts to apply the theories to humans
Edward O. Wilson
Sociobiology: The New Synthesis1975
Some Types of Evolutionary Psychology Theory
Systems Theory
Kin Selection/Inclusive Fitness Theory
Parental Investment TheoryAltruism Theory
Sociability Theory
Multilevel Evolutionary Theory
Kin Selection/Inclusive FitnessIndividuals will tend to invest in
others in proportion to their degree of relatedness.
Degree of relatedness is calculated using the proportion of genes shared in common.
Kin Selection/Inclusive Fitness Theory
== = = =
1/2
= =1/2
1/2
1/2 1/2
Cousins Brother EGO Sister Cousins
1/2
1/21/2 FaSi FaBr Father Mother MoSi MoBr
Parent-Child ½ Grandparent-Grandchild ¼ (½ x ½)
Aunt/Uncle-Niece/Nephew ¼ (½ x ½) Cousin-Cousin 1/8 (½ x ½ x ½)
Males Females
Parental Investment TheoryRelative Contributions of Males and Females to Offspring
Gamete size and contribution to embryo
Minimum time investment to birth of a child
Minimum emotional investment to autonomous healthy child
Minimum economic investment to autonomous healthy child
1/200,000 of an egg
A few minutes
None
None
200,000 times larger
Nine months
5 to 7 years
5 to 7 years
Parental Investment TheoryMale vs. Female Mating Strategies
What characteristics are most sexy?
Males FemalesYouth, Beauty Power, Wealth
Very important. The female needs help with the large time, emotional and economic investments she must make to produce a healthy adult offspring. She would like her mate to stick around and help.
It varies. Commitment to a single female is one of many strategies for a male. The male can offer fidelity to a single female to help support their offspring. This is only one of the male options. At the other end of the spectrum is “free copulation” leaving females to care for offspring.
How important is exclusivity
and
commitment?
Parental Investment TheoryHypotheses about The Range of Male Strategies
The Swinger: Males who attract lots of females who are willing to have sex with them are better off not making a commitment to a single female. They will hope that some of the women with whom they copulate will get pregnant, and that the women will find a way to support/raise the child, either alone, or with the help of another male. This way they have the potential for having large numbers of children in whom they will have invested very little.
The Nerd: Males who do not attract lots of females who are willing to have sex with them can offer commitment as an inducement for sex. They promise long term fidelity and support for the female and her offspring, allowing the female to have more children, or to raise more successful children because she has the time, emotional and economic investments of a male on whom she can count.
Parental Investment TheoryHypotheses about Female Strategies
Females will be attracted to wealthy, powerful males who can help them support and raise their children. This will be especially true in cultures where males control resources. They may tolerate such men having multiple wives or partners as long as they and their children are supported.
Females will be less exclusively monogamous when they have access to economic resources or earning power themselves. However, they will never be as promiscuous as the most promiscuous males.
The risk of pregnancy and the investment that follows conception for women will make them more careful about sexual partners, and more interested in commitment from partners than will ever be true for males.
Recommended