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
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
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. 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. 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. 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
23. 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)
24. 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
25. 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)
26. 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
27. 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)
28. 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
30. 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
31. 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
32. 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