The Role of Variation in Cultural Change -Abstracts
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F. John Odling-Smee
Where does human cultural niche construction fit in?
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.
Why Cultural Elaboration? An Evolutionary Perspective.
Cultural elaboration – the investment of time and energy into activities that do not have a clear role in enhancing survival or reproduction – is a common feature among complex societies and often highly visible archaeologically (e.g., mounds, grave goods of exotic materials, etc.). Such costly activities need to be explained at a theoretical level, and evolutionary models offer such a theoretical framework, but further refinement is needed. While many forms of cultural elaboration appear not to be adaptively neutral because they divert time and energy away from subsistence pursuits, we need to develop the analytic tools to show that they are not. There are many different forms of cultural elaboration and we need to ensure that the variability we are interested in explaining is accommodated by models we use. Evolutionary models need to include considerations of age structure and fertility in human populations, and we need better analytical tools to assess whether the economic costs of cultural elaboration have demographic and selective consequences in specific empirical cases. Many expressions of cultural elaboration clearly involve group-level activities, so evolutionary models that only consider benefits to individuals need to be extended to consider potential benefits to groups of individuals and the integrative mechanisms that facilitate large-scale cooperation. These refinements will require that archaeologists shift from describing modal tendencies to documenting variation in terms of frequency across time and space.