AHS13 Geoffrey Miller Sexual Fitness and Women's Fertility Cycles


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AHS13 Geoffrey Miller Sexual Fitness and Women's Fertility Cycles

  1. 1. Sexual Fitness and Women’s Fertility Cycles Geoffrey Miller
  2. 2. DNA: wonderful but fallible for 3.5 billion years
  3. 3. DNA: wonderful but fallible replication • http://www.youtube.com/watch?v=4jt mOZaIvS0
  4. 4. Sex evolved 1.2 billion years ago: easier to spread good mutations, purge bad mutations from offspring Bacterial conjugation via pilus
  5. 5. Eyes evolved 543 m.y.a.  mate choice  Cambrian explosion of biodiversity
  6. 6. Evolution = natural selection for efficient survival + social & sexual selection for conspicuous signals
  7. 7. Every primate face is a different set of sexually-selected ornaments
  8. 8. Every primate face is a different set of sexually-selected ornaments
  9. 9. Every primate face is a different set of sexually-selected ornaments
  10. 10. Averaged female faces across Europe
  11. 11. Costly signaling principles allow vast range of innovative signals  Conspicuous waste (size, materials, energy, time)  Conspicuous precision (typicality, symmetry, pattern repetition, fit, finish)  Conspicuous creativity (novelty, variety)  Conspicuous reputation (status, prestige, familiarity, branding)
  12. 12. Physical fitness indicators Morphological Face Height Muscles Fat Deposits Health Behavioral Sports Dance Sex Michael Jordan Maria Sharapova
  13. 13. The human brain: a fitness-indicator wonderfully vulnerable to mutations Most of the genome is expressed in the brain; Most harmful mutations disrupt brain function somewhat
  14. 14. Mental fitness indicators Semi-practical, Semi-ornamental Intelligence Language Mental Health Status Wealth Moral Virtues Mostly Ornamental Creativity Music Art Humor Happiness
  15. 15. Pair-bonding & mutual mate choice for over a million years • Like socially monogamous birds • Mutual display of fitness indicators • Assortative mating for mate value & status • Yields sexual equality in many indicators & signaling motives
  16. 16. Women’s ovulatory cycles Fertility (probability of pregnancy given copulation) Days into cycle 
  17. 17. Women at higher fertility phase seek to poach better genes: • More mate search & socializing, less eating & staying home • Avoid rape & incest more effectively • Less satisfied with long-term partner if he’s lower fitness • More fantasies, flirtation, dancing, & short-term affairs with higher-fitness men • Mate-guarded more closely by lowerfitness partners • Hormonal contraception (the Pill) eliminates all this
  18. 18. Women at higher fertility phase show stronger preferences for ‘good genes’ traits in males Physical fitness indicators • Body height, muscularity • Facial masculinity, attractiveness • Deep voice • Healthy body scent Mental fitness indicators • Dominance & assertiveness • Verbal & artistic creativity • Good sense of humor
  19. 19. Women at higher fertility phase are rated more attractive by men • • • • • • Earn higher tips per hour as lap-dancers (Miller, Tybur, & Jordan, 2007) 400 350 Dollars Earned Per shift Skin condition Facial attractiveness Body shape Body scent Clothing more stylish & revealing • Voice pitch & timbre • Verbal creativity 300 250 Normally Cycling 200 Pill Users 150 100 50 0 Menstrual Fertile Cycle Phase Luteal
  20. 20. Cryptic female choice • Co-evolution of male and female genitalia and preferences • Females evolve to favor male traits for better copulatory courtship, as indicators of genetic quality and phenotypic condition: – larger, more complex male genitalia – longer, more vigorous copulation – repeated ejaculations over time
  21. 21. Cryptic female choice favors more complex male genitalia Damselfly penis
  22. 22. Clitoral anatomy for cryptic female choice Complex deep structures, not just the glans clitoris • circle the vagina • assess penis girth & length, & copulatory vigor • project to different cortical areas (Komisaruk et al., 2011)
  23. 23. Female sexual pleasure as a mate choice system • Female orgasm should: – differ across males & situations – 100% ‘reliable’ would be indiscriminate – promote repeated mating with favored males – not necessarily increase fertility from one-shot copulation through ‘upsuck’ • Differential sexual pleasure should predict partner choice regardless of woman’s base rate of orgasm
  24. 24. Female preferences for longer-than-average penis sizes; aversion to small penises • • • • • • • • Francken et al. (2002): Netherlands Stulhofer (2006): Netherlands Dixson et al. (2007a): China Dixson et al. (2007b): Cameroon Dixson et al. (2010): New Zealand & California Brody & Weiss (2010): Czechoslovakia Shaeer et al. (2012): Middle East Costa, Miller, & Brody (2012): Scotland: Women who prefer longer penises are more likely to have vaginal orgasms (but not clitoral orgasms)
  25. 25. Mautz, Wong, Peters, & Jennions (2013) PNAS • 105 Australian women rated attractiveness of life-sized projected male bodies • Higher shoulder-to-waist ratio strongly attractive • Strong & equal effects of height and penis length
  26. 26. Erectile function as a sensitive fitness indicator Poor erectile function; • is a sensitive early marker for cardiovascular disease (Gazzaruso et al., 2011) Good erectile function: • predicts lower risk of heart attack, stroke, diabetes (Jackson et al., 2010; Nehra et al., 2012) • reveals better physical fitness in men aged 1840 (Hsiao et al., 2012) and 40-75 (Agostini et al., 2011) • reveals lower oxidative stress & inflammation (Meldrum et al., 2012) • reveals aerobic capacity and exercise level (Kratzik et al., 2009) • is a general marker for male health (Salonia et al., 2012)
  27. 27. Copulation as a risky activity for low-fitness males • Bohlen et al. (1984): copulation as a low-energy activity, c. 3-5 METS (like fast walking)? • Cf. Levine et al. (2012): AHA statement ‘Sexual activity and cardiovascular disease’: Copulation moderately increases risk per minute of angina (‘coital angina’), myocardial infarction (heart attack), and sudden death from ventricular arrhythmia
  28. 28. Distance running, persistence hunting, aerobic warfare favor female choice for prolonged high-wattage copulation?
  29. 29. Sexual coevolution between female choice and male traits Vaginal & deep clitoral orgasms favor physical fitness indicators:  Longer, thicker, smoother penis  Prolonged, aerobic copulation Superficial clitoral orgasms favor mental fitness indicators:  Mating intelligence, sexual experience, kindness, patience Extended sexuality across ovulatory cycle favors general health indicators:  Repeated copulations before pregnancy is likely
  30. 30. Natural fitness indicators under-valued in modern societies Physical fitness indicators: • Consumerism: – a few pro athletes & movie stars – mass sedentary obesity & sexual dysfunction • Paleo: functional fitness & sexual fitness for all
  31. 31. Natural fitness indicators under-valued in modern societies Mental fitness indicators: • Capitalism: – 1% rich, educated careerists & entertainers – 99% service workers, media addicts, & bored spouses • Paleo: mating intelligence & courtship abilities for all
  32. 32. Questions?