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Outline: Biology – One human nature

Outline: Biology – One human nature. Evolution of the human species Evolved Predispositions Selfish behavior Reciprocal Altruism Kin-Based Altruism Gender Asymmetry in Parenting Implications of gender asymmetry: sex differences in mate choice and family roles Individual Differences

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Outline: Biology – One human nature

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  1. Outline: Biology – One human nature • Evolution of the human species • Evolved Predispositions • Selfish behavior • Reciprocal Altruism • Kin-Based Altruism • Gender Asymmetry in Parenting • Implications of gender asymmetry: sex differences in mate choice and family roles • Individual Differences • Hormones and Behavior • The Importance of the Situation

  2. The social phenomena that sociologists study are a complex result of many factors • One important factor is our shared human nature – rooted in our species biology

  3. Evolution of the human species • Humans like all species are a product of evolution • Our species evolved in Africa, during the Pleistocene about 2 million years ago. • This is referred to as the Evolutionary Environment (E.E.)

  4. In the E.E. there was selection for both physiological traits (e.g. body shape) and behavioral traits (e.g. bi-pedalism, food preferences). • These traits solved adaptive problems in the evolutionary environment i.e. they helped our ancestors survive and reproduce

  5. What was the evolutionary environment like?

  6. We were hunters and gatherers on African Savannah • We lived in small, nomadic groups of not more than 100 or so people

  7. Examples of adaptations to the evolutionary environment • Taste for sweets, fats and salts

  8. Fear of snakes

  9. Then, about 50,000 years ago, our species left Africa and colonized all the landmasses of the world

  10. When people settled in different areas, there was some evolution in response to local ecological conditions • Skin color, hair texture, shape of nose etc.

  11. Western Europeans faced selection for light skin because of cloudy conditions in northwestern Europe

  12. These genetic differences between groups are very small compared to the genetic similarities between groups

  13. In the E.E., behavioral and psychological traits that helped our ancestors survive and reproduce were selected for. • Also known as evolved predispositions

  14. Evolved predispositions • Other terms – adaptation, psychological mechanism, tendency. • Definition: An evolved predisposition exists in the form it does because it repeatedly solved a specific problem of survival or reproduction over evolutionary history.

  15. They are just predispositions! • They don’t determine behavior! • Actual behavior is a product of both the predisposition and the context, including the social context.

  16. Predisposition Behavior Context Inc. culture!

  17. Evolved predispositions • Selfish behavior • Individuals who were somewhat self interested in the evolutionary past were more likely to survive and reproduce than other individuals • Eg. Individuals who made sure they had enough to eat, drink etc. were more likely to survive and reproduce!

  18. Reciprocal altruism • Stone age people couldn’t make it on their own – they needed other people • Hence the selection of traits favoring reciprocal altruism – “you scratch my back and I’ll scratch yours.”

  19. Kin-based altruism • Individuals who in the evolutionary past helped their genetic relatives left more descendants and genetic relatives than individuals who did not • Selection for traits that predisposed individuals toward kin-based altruism (Hamilton 1964). • Includes a cognitive or psychological bias toward kin.

  20. Gender asymmetry in parenting • Female fixed investment in offspring are much greater than male fixed investment in offspring • Females have the larger and costlier gamete, must bear costs of gestation, childbirth and nursing • Limited number of years of childbearing

  21. Greater fixed investment of each female in each of her offspring • In the evolutionary environment, the behavioral strategy most likely to lead to successful reproduction for females was the “mom” strategy • Make sure each child survives and thrives

  22. Male fixed investments are relatively trivial. • Many opportunities to father offspring

  23. In the evolutionary environment, TWO strategies could lead to successful reproduction for males – the “dad” and “cad” strategy • So males may be “dads” and invest in their offspring • But can also “free ride” on the investments of females – be “cads” and still get their genes in the next generation

  24. Sex differences in parenting • Differential fixed investments by sex promote gender asymmetry in parenting • Worldwide, mothers are much less likely to abandon their children than fathers.

  25. Sex differences in mate preferences • Differential fixed investments in offspring encourage males and females to have different mate preferences. • Women are likely to be interested in committed men who are going to stay around and invest

  26. Also interested in males who can provide resources to future children, and are stable and dependable so as to continue to invest in children in the future. • Also looking for the best second set of genes they can find.

  27. Males are going to be less interested in resources and status in a mate • More interested in youth and beauty in a mate, as these are correlates of the ability to bear children • Also interested in fidelity, given the problem of paternity uncertainty

  28. Cross cultural studies suggest that these sex differences in mate preferences exist in all cultures • Females disproportionately prefer status and resources in a mate, males disproportionately prefer youth and beauty

  29. Lead to social norms and roles • Promote the emergence of roles and norms that support women as primary care-givers to children • Promote the emergence of more instrumental roles for men

  30. Not everyone is the same! • What is true of the average is not true of every individual • Twin studies (of identical twins reared apart) show that individual differences may be genetically based.

  31. Hormone levels influence behavior, and there are differences among individuals

  32. The situation matters! • Predispositions toward selfish behavior, reciprocal altruism, and gender asymmetry in parenting influence behavior in the context of particular situations

  33. Example: maternal commitment • In hunting and gathering societies, mothers could not take care of two infants close together in age. • Would kill the second one so the first would survive and thrive • Better than having both children die

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