Gene-culture coevolution How might genetic and cultural evolution interact? When correlate, when oppose? Can cultural transmission alter selection pressures? Given social learning, can population genetic structure influence rates of cultural transmission?

Gene-culture coevolution Gene-culture theory Individual: genotype & cultural trait “Phenogenotype” dynamics: Mendelian inheritance & cultural transmission

Gene-culture coevolution Feldman & Laland Gene-culture coevolutionary theory. Trends Ecol. Evol. 11:453. Evolution different than in acultural populations

Gene-culture coevolution Cultural transmission can modify selection pressures, alter evolution Selection differs by presence/absence of cultural trait Dairy farming: lactose digestion

Selection differs by presence/absence of cultural trait: Dairy farming Lactose absorption Adults: variation in milk digestion Among-populations Lactose absorption strong genetic basis Dominant autosomal trait Many, but not all, populations: Only 20% adults digest milk

Lactose absorption Note correlation: lactose absorption & history of dairy farming Culture: Dairy, app YBP Gene: Absorbers 90% of adults, Why allele so common in population with history of milk consumption?

Lactose absorption Dairy farming culture: selective pressure for milk digestion ? Adsorption allele A vs a Two cultural states (use, not-use milk) 6 phenogenotypes Vertical cultural transmission only Fitness advantage milk digestion assumed

Lactose absorption Advance of allele A depends Strong enough cultural transmission Fitness advantage milk use Milk use does not always spread, despite fitness advantage; Culture can inhibit selection

Lactose absorption Must combine allele A and milk-use culture to gain (assumed) fitness advantage. Critical transmission fidelity to promote allele Gene-culture coevolution end

Natural selection may oppose culture Excess female mortality Preference for sons in some areas Cultural attribute Greater female mortality before age first reproduction

Excess female mortality Gene: SRVX, “femaleness” gene Distorts sex ratio in humans Can cultural bias favoring males influence selection on sex-ratio distorter gene ?

Excess female mortality Model: Cultural  sons > daughters Know (sex-ratio evolution): Increased fitness female offspring Rarer sex has more mean offspring Gene for daughters > sons favored

Excess female mortality N-person game equilibrium: IF parents have more children to compensate for lost daughters: Female-bias in sex ratio at birth compensates for cultural bias favoring males Adult sex ratio unbiased

Excess female mortality Other cultural practices: adjust sex ratio & no. offspring Can bias primary sex ratio toward males Culture profoundly affects evolution of sex-ratio gene

Gene-culture coevolution Horizontal cultural transmission may promote group selection in some environments May counter individual selection within groups Conformism: new model human altruism?