How does sexual selection influence human mate choice

How does sexual selection influence human mate choice? 1

6/25/08: The Evolution of Human Behavior: Mate Choice Lecture objective: Generate adaptive hypotheses and predictions about human mate choice 2

Caveats to studying human behavior from an evolutionary perspective: 1. Humans do not consciously do things to increase their inclusive fitness. (Neither do non-human animals. ) Those organisms that tended to behave in a way that maximized their fitness tended to leave more offspring who also behaved that way. 2. Saying a behavior is adaptive does not mean it is morally/ethically right. 3. Saying a behavior is adaptive does not mean it is genetically determined/developmentally inflexible. 4. Not all human behavior is adaptive in modern society. However, it could have been adaptive for our ancestors in the recent past (EEA). 3

Darwin recognized that some individuals have a reproductive advantage over others Sexual selection: a form of natural selection that occurs when individuals vary in their ability to obtain mates relative to others of the same sex What generally limits the reproductive success of females? What generally limits the reproductive success of males? 4

In pre-industrial humans, polygyny was the norm Frequency of marriage types across cultures (pre-industrial) 5

Choosiness in women vs. men Hypothesis: In humans, females are the Prediction: Women should be Prediction: Women should have But in general, both men and women appear to be choosy when seeking a long term mate. Why might this be? 6

Adaptive mate preferences in humans Based on your knowledge of sexual selection, if humans show adaptive preferences for mate qualities, then: Men should generally prefer women who exhibit signs of Women should generally prefer men who exhibit signs of and 7

What men look for in women: fertility (beauty, youthfulness) Hypothesis: The (stereotypical) male preference for the female hourglass figure is adaptive Prediction: Women with an hourglass figure should be 8

What men look for in women: fertility (beauty, youthfulness) In 37 cultures (out of 37 studied), males prefer mates _______ Hypothesis: Male preference for younger females is adaptive 9

What men look for in women: fertility (beauty, youthfulness) The quality of nuptial gifts often correlates with aspects of mate quality Hypothesis: The amount of resources invested in an engagement ring is adaptive Prediction: Males should buy more expensive engagement rings for _______________________ typically received a more expensive ring 10

Importance of female attractiveness is no myth… Prediction: Male preference for attractive females should be culturally universal In folk tales, female protagonists were typically: 11

What women look for in men: wealth Women advertise for _____ Arizona Higher income increases a male’s __________ (NPC = number of potential conceptions) India 12

What women look for in men: health Women generally prefer men with features that: __________ (higher levels of testosterone) Low T Med. T High T ___________ (better developmental stability) Normal Asymm. Perfect Sym. 13

What women look for in men: health Women generally prefer men with a masculine facial structure, which is linked with high levels of testosterone Prediction: If this preference is adaptive, women in the _____ of their cycle should be more likely to prefer men with a masculine facial structure Why? 14

What women look for in men: health In Jamaica (compared to Britian), parasite load is higher, medical care is less common, and paternal care is more rare Prediction: If women’s preferences for male facial structure is adaptively linked to health, then ____ women should prefer more masculinized faces than _____ women 15

(Thankfully), beauty is in the eye of the beholder 16

Do humans have cryptic female choice? What is the function of female orgasm (FO)? Non-adaptive hypothesis: FO is an _____________ Adaptive hypothesis: FO is an adaptive means by which females can manipulate the ______________ Prediction: Women with more symmetrical mates will be more likely to have copulations that are accompanied by FO 17

Are female preferences for male body odor adaptive? Products of the MHC (major histocompatibility complex) play an important role in immune function The “smelly t -shirt” experiment Prediction: Non-pregnant women should prefer the body odor of men who are genetically ___________ Why might this occur? 18

Is social “copying” of mate judgments adaptive? Prediction: Female choice should promote _____ attitudes (by women) toward men who other women find attractive (hunk) Prediction: Within-sex competition should promote _____ attitudes (by men) toward men who women find attractive (jealousy) 19