Human sociobiology 1

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Human sociobiology (1)

• MSc ACSB 2005/06
• Session 15

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Contributions of SB to HSB ??

• Aid-giving explained by kinship/ inclusive
  fitness, reciprocation, (?reputation, etc.)
• Mate choice, mating strategies
• Parental investment, step-parents, sex ratios
• Life history strategies
• Evolved mental modules e.g. cheat detection
• Evolutionary analysis of man as a primate

3
Changes since early HSB

• Helena Cronin The ant and the peacock
• Early HSB emphasized IF, aid-giving, kin
  relations in warfare, etc.
• We now know that IF is only one (?minor) factor
  accounting for animal cooperation
• In ASB and HSB, mate choice/mating strategy has
  become a more sexy topic

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Problems with HSB

• Kitcher (1985) Vaulting ambition
• HSB tries to explain too much. Predictions
• may trivialise important issues (rape, child
  neglect)
• legitimise bad behaviour, or appear to do so
• Are vague, often changed if they dont work (so
  dont definitively test SB theory), poorly
  worked-out
• Buller (2005) TICS article
• Poor-quality evidence needs higher standards of
  scientific argument

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Is sociobiology poor science?

• ?Looks for Darwinian explanations where none
  required
• ?Cloaks the obvious with an appearance of
  scientific analysis
• Consider two examples
• Adolescent acne
• Female-male differences

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Acne an adaptation to protect from teenage sex?

• Bloom (2004) Medical Hypotheses 62, 462-469
• Acne is not an infection action at puberty of
  hormones on (?distinct) follicles
• On face - visible causes disgust (protects from
  sexual advances). Resolves naturally in early 20s
  when prefrontal cortex is fully mature
• Not a disease, but a normal process. Adapted to
  ward off potential mates during newly-evolved
  phase of adolescence. Resolves when individual
  has reached age of reproductive and emotional
  maturity

7
Sunday Sport science?

• Clark Hatfield I have been noticing you around
  the campus. I find you very attractive. Would
  you (Percentage who said Yes)
• Go out with me tonight M50 F50
• Come to my apartment tonight M69 F 6
• Sleep with me tonight M75 F 0
• Alternatives
• EP explanation Sex differences in parental
  investment-gt choosiness in women
• Suggestion from the audience Men are slime
  (Pinker)

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Sex differences in mate choice strategies

• Differences in male vs. female mate choice
  strategies are widely documented (Buss, Kenrick,
  etc.) reflect sex difference in PI
• Also differences in standards for long- vs
  short-term relationship
• But your granny knew this! No need for HSB/EP
• HSB/EP does lead to some novel predictions and
  studies

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Male and female choices do they reflect
quality?

• Breast size and figure in women if C20
  preferences reflect quality, why did Rubens paint
  and value fleshy nudes?
• ? Just a matter of fashion
• ? Cultural differences in preferences that
  reflect the adaptive context (e.g. reliability of
  food supply)

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Large-breasted, slender women more fertile
Jasienska et al (2004) studied 119 women aged
24-37 years, with no fertility problems Measured
Estrogen and Progesterone, two key reproductive
hormones Left panel Salivary E2 ? women with low
WHR (mean, sd 0.67, .015), women with high WHR
(0.80, .028) Right panel Salivary P ? low WHR,
high WHR
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One ornament studies

• Thornhill Grammer (1999) EHB 20, 105-120. The
  body and face of a woman one ornament that
  signals quality?
• Face, front (face covered) and back views of nude
  women correlate for attractiveness. One ornament
  signalling mate value (oestrogen, developmental
  symmetry)
• Feinberg et al. (2005) EHB 26, 398-408. The
  voice and face of a woman... Women who have
  higher-pitched (more attractive) voices have
  faces that are themselves more attractive. Less
  masculine women have higher reproductive fitness.

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Voices act as markers for FA

• Hughes et al (2002) EHB 23, 173-180 Voices of SS
  varying in FA assessed by raters who did not see
  the SS. Symmetrical SS had more attractive
  voices.
• Puts (2005) EHB 26, 388-397 Lower F0 in male
  preferred in short term, but not long term,
  mating contexts. F0 had greatest impact on ST
  attractiveness in fertile phase of ovulatory
  cycle
• So voice pitch, as with face shape, may carry
  information about quality

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Why might faces, voices, or other ornaments, be
honest signals of quality?

• Hormones affect the immune system. High
  testosterone level compromise immune defence
  high quality males can cope (e.g. Duffy Ball,
  2001, PRSB 269, 847-852 on starlings)
• Estrogens ? may have parallel effects
• Face growth depends on hormones voices also
  reflect hormone levels
• Costs of having a low-WHR figure in women?

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Faces disease (1)

• Thornhill Gangestad (2006) EHB 27, 131-144
• Facial asymmetry correlated with number of
  respiratory infections and days infected
• Body FA correlates with number of respiratory
  infections
• No correlations with stomach infections
• Facial attractiveness - no correlations with
  disease

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Faces disease (2)

• Hume Montgomerie, 2001, EHB, 22, 93-112
• FA in face, body, fingerprints, separately
• Facial attractiveness negatively related to
  overall asymmetry
• For women it reflects BMI, past health problems
• Men high attractiveness linked to high SES
  rearing environment() Women the reverse (ns)
• So facial attractiveness may signal different
  aspects of quality in women and men

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More than 1 female strategy?

• Females may play a mixed strategy
• Differences between preferences of women scoring
  high and low on scale of sociosexuality
• Differences in womens preference between period
  of highest fertility and rest of menstrual cycle.
  (Pill users are like latter group)

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Pupil sizes and mate choices

• Tombs Silverman (2004) EHB 25, 221-228
• Expanded pupils known to enhance attractiveness
  in both sexes
• But some females prefer men with large pupils,
  others prefer medium pupils
• Large-pupil preference linked to womens tendency
  to prefer bad boys rather than nice guys as
  dates
• Suggests a strategy-differences among women
  reflecting their response to the male
  attention/attraction implied by the largest pupil
  size

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Ws rating of M display

• Gangestad et al. (2004) Psychological Science
  15(3), 203-207
• M videoed in competitive date-choice context W
  see 1 min, rate as Short- or Long-term mate
• Social presence composed, athletic, eye contact,
  no self-deprecation, no downward gaze, doesnt
  present self as nice guy
• Direct intra-sexual competitiveness e.g., slags
  off competitor, asserts superiority, not just
  himself, no laughter, doesnt say he has a nice
  personality
• Composite SP-DIC rating peaked at day 11 of
  menstrual cycle, but only for Short-term mate

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Effect of consequences and culture

• Male-female differences in behaviour or stated
  preference may have (historically) been
  compromised by
• Risks (e.g. pregnancy) for female who shows no
  self-restraint
• Cultural conventions that permit males and did
  not permit females to engage in certain behaviour
• Limitations imposed by families

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Fantasy, and gay relationships, as tests

• Ellis Symons showed differences in sexual
  fantasy womens less visual, more focussed on
  emotion and romance
• Males/females want different things from
  relationships
• Symons differences in length of gay
  relationships (males stereotypically very short,
  females much longer)
• (once cultural constraints and risk of having
  children are both removed) male and female brains
  have evolved to value different things in a
  relationship

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References

• Busss Evolutionary Psychology deals with these
  issues extensively.
• See also Betzig (ed.) Human Nature combines key
  articles and commentaries
• For next time J. Diamonds books Guns, germs and
  steel, and The rise and fall of the third
  chimpanzee