Gene-culture coevolution Genetic evolution Dynamics allele frequencies Includes natural selection Populations adapt Behavioral ecology Try understand behavioral diversity: adaptations to environment
Gene-culture coevolution Cultural evolution Dynamics cultural traits Social learning Phenotypic plasticity No. transmitters/receiver Try to understand cultural diversity Cultural traits need not be adaptive
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 Alleles: parent to offspring Cultural transmission: vertical, horizontal or oblique frequency dependent (follow majority)
Gene-culture coevolution Importance of gene culture theory? Feldman & Laland. 1996. 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 1. Selection differs by presence/absence of cultural trait Dairy farming: lactose digestion
Gene-culture coevolution 2. Culture produces new evolutionary mechanisms Group selection? 3. Culture can induce time lags selection Alters gene-frequency dynamics
Selection differs by presence/absence of cultural trait: Dairy farming Lactose absorption Adults: variation in milk digestion Most low level of lactase Lactose absorption strong genetic basis Dominant autosomal trait Many populations: Only 20% adults digest milk
Lactose absorption Note correlation: lactose absorption & history of dairy farming Culture: Dairy, app. 6000 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: Rate of vertical cultural transmission Offspring milk users use milk & Fitness, Given dairy culture
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 Cultural transmission depends on genotype Strength cultural transmission influences evolution by natural selection Gene-culture coevolution
Gene-culture coevolution 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?