Evolve 7
- 1. Evolution and Human Behavior Sociobiology: The New Synthesis (1975) by E. O. Wilson A total of 26 chapters, the last one on human beings Controversy followed: Culture vs Biology
- 2. Misunderstandings About Sociobiology Human beings are not concerned about inclusive fitness: We often don’t know what motivates us, like food preferences and mate preferences Much of human behavior is not adaptive: The concept of the Environment of Evolutionary Adaptation (EEA) Sociobiology is a justification of racism and elitism: Confuse what is with what should be
- 3. Evolutionary Psychology Assume the mind is “modular” made up of specialized circuits Designed to solve re-occurring problems from the EEA Domain specific Analogy to a Swiss Army knife
- 4. Wason Selection Task You are the new file clerk at the local high school. You must verify that documents conform to a certain rule. The rule is: If a person has a “D” rating, then his documents must be marked code “3”. Which of the following do you need to see additional information? 1. “D” 2. “F” 3. “3” 4. “7”
- 5. Wason Selection Task You are the bouncer at a bar. You need to be sure that the law is not being broken. If a person is drinking beer, the he must be over 21 years old. Which of the following do you need to see additional information? 1. drinking beer 2. drinking coke 3. 25 years old 4. 16 years old
- 6. Logical Structure is the same If P then Q. Logically the rule for testing the truth involves P and not- Q. The content makes it easy for the beer drinking example, much harder for the file clerk example The brain is specialized to detect cheaters in social interactions.
- 7. Arbitrary Culture Theory In opposition to evolutionary explanations of human behavior Claims that most behavior is a reflection of traditions and unique customs of a particular people Example: High rates of adoption in the islands in the central Pacific ocean
- 8. Evolutionary Explanation of Adoption Adoption should be frequent when adopted children are related to the adopting parents
- 10. Proximate Mechanisms for Adoption Parental “instincts” are aroused for childless couples Inability to have children is most frequently given reason for seeking adoption In the EEA infertile women would likely be living with close relatives making “adoption” adaptive Many childless women and couple treat pets (usually dogs) like children
- 12. What Do We Want in a Mate? From the standpoint of fitness, we want successful offspring Males want a female who will become pregnant and have a healthy baby Women want men who will help raise the offspring
- 13. Male Mate Preferences Youth: Females maximum fecundity is at about 26 years old Waste-to-hip ratio of .7: Also an honest marker of fertility and health Narrow waist, large breasts: Also correlated with fertility
- 15. Mate Preferences and Ovulatory Cycle Humans females are supposed to be “Concealed Ovulaters” giving no sign of their fertile period Tee shirt studies show that males prefer the smell of ovulating women over non-ovulating Males rate faces of ovulating women as being more attractive
- 16. More on Ovulation Cycle Women show more skin and touch men more during their fertile period Women prefer a masculinized male face during their fertile period and non-masculinized otherwise Paradoxically, women rate their own attractiveness lower during their fertile period
- 17. Female Mate Preferences Men who have resources: Professional, good job, educated Men who are older Men who are high in status Men who are athletic Men who have masculine faces (testosterone correlated)
- 18. Masculine Faces Testosterone levels during development correlate with masculinized face High testosterone may also signal a strong immune system Testosterone has a pleitropic effect: High levels early in life may shorten life span Increasing masculinity from left to right in next slide
- 21. Income and Earning Power Data from surveys show females rate earning potential much higher than males, across 37 countries (David Buss) Data from “Man seeking woman” and “Woman seeking man” ads also confirm the difference
- 23. Mate Preferences for Both Sexes Kind and Considerate Good sense of humor Symmetry of face and body: A marker of good developmental homeostasis
- 24. Conditional Mate Preferences Self rated attractiveness is positively correlated with preference for attractiveness in a mate
- 26. Conditional Preferences Minimum acceptable intelligence for different levels of involvement (50% means at the middle of the intelligence scale for the population
- 27. Clark and Hatfield Study Had an attractive male or female experimenter approach a member of the opposite sex Experimenter ask the stranger, would you like to go out with me?, or would you like to come to my apartment tonight? Or would you sleep with me tonight? Females: 50%, 10%, 0% said yes Males: 50%, 60%, 65% said yes
- 28. Number of Partners Males desire more partners in their lifetime than do females Males would engage in sex sooner in the relationship than females
- 31. Jealousy Males are concerned with paternity of offspring Females are concerned with help raising offspring Threats to these characteristics give rise to jealousy—becoming upset
- 32. Which is more upsetting? Imagine yourself in a committed relationship and your partner becomes involved with another person. Which is more upsetting? You partner has a passionate sexual relationship with that person Your partner has formed a deep emotional bond with that person
- 33. Which is more upsetting? Imagine the same committed relationship, but now your partner becomes involved with a person of the same sex as your partner. Which is more upsetting? You partner has a passionate sexual relationship with that person Your partner has formed a deep emotional bond with that person
- 34. Results Heterosexual relationship: Males say sex 60%, females say sex 30% Homosexual relationship: Males say sex 50%, females say sex 80%
- 35. Sex Differences in Spatial Abilities Division of labor: Hunters and gatherers To be a good hunter must be able to keep track of where the prey is, where home is and how to get there: Spatial rotation task. To be a good gatherer must remember where food was located: Plants don’t move around. Spatial memory task
- 37. Human Conditional Mating Strategies Recall conditional strategy of the scorpionfly: guard insect, produce saliva, forced copulation Is human rape a conditional mating strategy? Or is it males way for controlling females by fear?
- 38. Characteristics of Rape Females are more likely to become pregnant by rape than by consensual sex If rape is an adaptation, then most fertile women should be most often raped If rape is male intimidation, then it should be most frequent in women who are in powerful positions, and should be comparable to murder
- 40. Rape as a maladaptive side effect Male’s motivation for many sexual partners and quick sexual arousal lead to over-expression of sexual behavior Predicts that rapists should have more consensual sex than average, which is supported by some data Final explanation of why rape occurs is not done
- 41. Parental Care Certainty of parenthood affects amount of parental (grand parent) investment How much support have you received from your grandparents? Mother’s mother has greatest certainty of parenthood, father’s father the least certainty, and father’s mother and mother’s farther are intermediate
- 42. % Students ranking each grandparent as most invested
- 43. Parental Resource Allocation Males must often compete for limited number of females Bridewealth is male giving resources to females family Dowry is female giving resources to males family Bridewealth is much more common, particularly in polygynous cultures
- 44. Inheritance Sons receive more inheritance from parents that daughters, particularly in polygynous cultures In monogamous cultures, sons are favored 58% of the time In polygynous cultures, sons are favored 80 to 97% of the time
- 45. Increased wealth increases the proportion of inheritance given to sons High levels of wealth increase a males chances of successful reproduction Data from Canada:
- 47. Biological vs. Non-Biological Parents Step children are usually not given as much parental investment as biological children Giving a child money to help attend college:
- 49. Step children are more at risk for child abuse than biological children Daly and Wilson data show that step child is 100 times more likely to be killed than biological child Child abused is also higher in stepchildren, especially young ones
- 51. Stone-age Mind in a Modern Society Many problems with today’s world may have been adaptations that were successful in our evolutionary past Eating sweet and calorically rich foods=obesity Oportunistically using resources = deforestation, overfarming,overfishing Producing tools and artifacts quickly and efficiently = pollution
- 52. Cooperation in hunting and other tasks = in-group—out-group mentality My group is good, the other groups I meet are not Ability to acquire information from experience = “bad” information is as easy to acquire as good. Chimps hunt in groups and return home after the hunt
- 54. The Future E. O. Wilson claimed in his book, Sociobiology: The New Synthesis in 1975 that evolutionary theory would transform the social and behavioral sciences Was he right?