Transcript A Mind Fit for Mating - University of Colorado Boulder

A Mind Fit for Mating
G.F. Miller
The Mating Mind, Ch 4 (2000)
Main Thesis
• Human mental abilities shaped by
sexual selection
• not natural selection
• Not necessarily optimal or rational
Sexual Selection
• Goal - choose mate with best genes for
offspring
• Feedback loops
– Runaway selection
– Fitness indicators
• Produces traits not optimal for survival
Runaway Selection
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Arbitrary preferences self-reinforce
Target sex must develop trait
Selecting sex need offspring with trait
Produces marked dimorphisms
Fitness Indicators
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Traits with strong correlation to overall fitness
Draw on large fraction of genome
Exogenous pressure for preference
Leads to exaggerated manifestation
Human brain
– Affected by 50% of genes
– Disproportionate energy use, x10-30
– Rapid tripling in size
Heritability of Fitness
• Mate selection only useful with
meaningful genetic variation
• Absent in evolutionary equilibrium
• But mutations, shifts in environment
Reliable Indicators
• Selective pressure to fake
• Only useful if
– Direct indicator of fitness
– Incur cost
• Handicap principle
– Wasting resources is reliable indicator of
fitness
Mental Traits as Fitness Indicators
• Traits not shared with other primates
– Music, humor, creativity
– (excess) language, altruism
• Characteristic of sexual, not natural,
adaptations
– Large individual differences, non-modular,
heritable, high costs, complex