The Role of Variation in Cultural Change -Abstracts

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F. John Odling-Smee

F. John Odling-Smee, Oxford University

Steve Lansing

The Domain of the Replicators: cultural evolution and the neutral theory

Darwinian models of cultural evolution consist of three types. If culture affects biological evolution, then cultural evolution is the heritable non-genetic transmission of anything that affects the reproductive success of individuals. Alternatively, culture may be viewed as a domain apart from biology, which evolves by Darwinian selection. Finally, in models of gene-culture co-evolution, selection occurs in both culture and biology. Evolutionary game theory offers a mathematical foundation for understanding evolution in all three cases, and interest in this approach is growing. Proponents argue that game theory is the appropriate tool whenever the success of an individual depends upon others. An evolutionary dynamic is added by modeling selection with the replicator equation, which instantiates Fisher’s Fundamental Theorem of Natural Selection (1930). But Fisher’s Theorem became obsolete in genetics after the discovery of DNA and has been forgotten by most geneticists. Geneticists and ecologists now infer selection by showing departure from Kimura’s null model of neutrality. Kimura’s approach shifts the level of analysis from the fitness of individuals to the effects of selection at the population level.

A central tenet of human behavioral ecology holds that facultative behaviors, such as dominance, produce fitness effects that are subject to cultural selection. But evidence for such selection is indirect, based on short-term statistical associations between behavior and fertility. Kimura’s neutral theory can be adapted to test for cultural selection in non-coding regions of DNA. Analyses of haplotype distributions defined by neutral microsatellites on the non-recombining Y-chromosome from 43 Indonesian communities show that differential selection among men is uncommon. Male dominance seldom translates into increased fertility over deep timescales, and short-term reproductive skew rarely produces long-term evolutionary benefits. The discovery that neutral processes explain most haplotype distributions in these communities parallels earlier results from the development of neutral theory in genetics and ecology.