ANTH151 Lecture Notes - Lecture 6: Female Promiscuity, Menarche, Orgasm
10 May 2018
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ANTH151 Lecture
VI: Human Sexuality in Evolutionary Perspective
Sexual reproduction
• Why not reproduce asexually? Some vertebrates do (100% female desert lizard species)
• Costs of sex: decreases potential species growth (only half species can reproduce) and getting
together can introduce risks
Why have sex?
• Recombination
• Inheritance that also introduces variation
• The Red Queen
• Defence against infection, parasites and other biological enemies
Sex as exaptation
• Human sexual activity, affiliative behaviour and even child rearing exceed what is necessary
for survival
• Birth spacing in foraging groups is usually four years minimum
• Our species like others uses the mechanisms of reproduction to solve other social and
psychological problems
• Classic case of an exaptation (but with moral complications)
What does sex do to evolution?
Sexual competition
• Whenever the evolutionary interests of the sexes diverge - conflict between the sexes
• A single ‘conflict trait,’ more useful for one sex than the other
• Anisogamy - energy that goes into male and female contribution different (size of egg and
sperm, female gestation)
Paternity v maternity records
• Mrs Feodor Vassilyev
• Russia
• 1700s
• 67 children
• 16 x twins
• 7 x triplets
• 4 x quadruplets
• Ismail bin Sharif
• Morocco
• Died 1727
• 867 children
Sexual selection
• Occurs when the potential rate of reproduction or parental investment differs between sexes
• In humans, at any time, many women are not in the ‘mating pool’ (pregnant, between
ovulation, nursing)
• Darwin proposed that traits might arise for intraspecific competition (among members of
species of the same sex)
• Direct competition favours weapons (secondary sex traits)
• In lekking, males father to compete
• Mate choice favours ornaments or display
• Signal cost can lead less desirable mates to evolve false signals
Human exceptionalism
find more resources at oneclass.com
find more resources at oneclass.com
• We may not want to believe that human sexuality is categorically not like other animals, and
it is true that humans are distinctive, but they are linked
Reductionism
• The idea, for example, that we can ignore human distinctiveness and understand sexuality
Sexual dimorphism
• In primates, the degree of dimorphism suggests whether polygynous or monogamous
• Differences between male and female often trace of sexual selection
• In some species, competition through display, song, provisioning, or next construction
• In primates, direct physical male competition and polygyny
• Extreme dimorphism suggests male competition and polygynous mating
• Relative equality suggests monogamous mating pattern in primates
• Human females are 80% the size of males
• Trend is toward convergence
Sexual homologous
Hormones and arousal
• Basic anatomy is female
• Hormones shape masculinisation and defeminisation of fetal tissue
• Through embryonic development, bodies diverge
• Same hormones present in both in different proportions (androgen and oestrogen)
Bodily arousal and homologous
• Male and female reaction very similar
• Homologous organs
• Blood flows into genitals causing swelling
• Similar changes throughout the body
Mating strategy
Risk of naturalising
• The danger of assuming that what is ‘natural’ is simple
• Compare to native language, problem with evolutionary psychology
• Many traits we’ve discussed all contribute to malleability
• Evidence suggests that mating, reproduction and child rearing variable and respond to
environment
Mating strategies
• Because men and women’s selective pressures are different, mating strategies differ
• Does evolution influence us to seek certain traits?
What do women want? An evolutionary psychology perspective
• Need enough food and support to
• Carry baby to term
• Feed baby once it’s born
• Take care of it as long as it needs
• In many primates, females form core of social group
Evidence?
• Dangerous assuming that behaviour we observe is universal ‘human’ or ‘resembles our
ancestors’
• Better to look to evidence in anatomy
Human Reproduction: Is Anything Natural?
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Some vertebrates do (100% female desert lizard species: costs of sex: decreases potential species growth (only half species can reproduce) and getting together can introduce risks. Inheritance that also introduces variation: recombination, the red queen, defence against infection, parasites and other biological enemies. Paternity v maternity records: mrs feodor vassilyev, russia, 1700s, 67 children, 16 x twins, 7 x triplets, 4 x quadruplets. Ismail bin sharif: morocco, died 1727, 867 children. Sexual selection: occurs when the potential rate of reproduction or parental investment differs between sexes. In humans, at any time, many women are not in the mating pool" (pregnant, between ovulation, nursing: darwin proposed that traits might arise for intraspecific competition (among members of species of the same sex) In lekking, males father to compete: direct competition favours weapons (secondary sex traits, mate choice favours ornaments or display, signal cost can lead less desirable mates to evolve false signals.
