Patterns and processes of cultural change [electronic resource]

The human capacity for culture may be viewed as a powerful adaptation that facilitates behavioral flexibility, responsiveness to changing environments, alteration of the environment itself, social coordination, and the retention of cumulative knowledge, skills and strategies over the generations. While the ability to engage in social learning and cultural transmission is underlain by genetically determined traits such as large brain size and the capacity for language, this does not mean that cultural traits themselves are genetically determined. Rather, cultural traits themselves may be learned, modified, and transmitted from individual to individual, or from group to group, across the generations. This thesis explores the interaction between human cultural change and natural selection, asking whether the same types of patterns and processes found by population geneticists can also be seen in cultural change. If so, then we have good reason to assert that cultural change may rightly be understood as a predictable evolutionary process. I approached this question from three directions, as follows. (1) Can natural selection affect the rate of cultural evolution? Can we infer positive or negative selection? We analyzed whether two sets of related cultural traits, one tested against the environment and the other not, evolve at different rates in the same populations. Using functional and symbolic design features for Polynesian canoes, we showed that natural selection apparently slows the evolution of functional structures while symbolic designs differentiate more rapidly. (2) Is cultural change subject to the same kinds of predictable patterns and processes as genetic change? We used a set of cultural data (canoe design traits from Polynesia) to look for the kinds of patterns and relationships normally found in population genetic studies. After developing new techniques to accommodate the peculiarities of cultural data, we were able to infer an ancestral region (Fiji) and a sequence of cultural origins for these Polynesian societies. In addition, we found evidence of cultural exchange, migration, and serial founder effect. Results were stronger when analyses were based on functional traits (presumably subject to natural selection and convergence) rather than symbolic or stylistic traits (likely subject to cultural selection for rapid divergence). These patterns strongly suggest that cultural evolution, while clearly affected by cultural exchange, is also subject to some of the same processes and constraints as genetic evolution. (3) Can human cultural choices alter the evolutionary process? We developed an agent-based simulation in which population growth is modeled as a function of resource production and allocation, to see whether the social structure of human societies can alter fertility, mortality, and overall demographic outcomes. The populations of societies that allocate resources equally among individuals were able to stabilize at carrying capacity, while societies in which different classes receive different fractions of available resources experience highly unstable populations and a high variance in fertility and mortality rates. This instability drives outward migration in search of resources, and consequently such class societies increase in frequency. When resource productivity varies from year to year, the spread of stratified societies is even more pronounced. These results suggest that stratified societies may have spread due to the demographic impacts of inequality. Greater differentials in fertility and mortality associated with socioeconomic inequality may create the potential for amplified individual selection in such groups, particularly for behavioral traits associated with obtaining access to resources and reproductive opportunities.

Keywords: Biological Sciences
Advisor: Feldman Marcus W. primary advisor. Thesis advisor
Ehrlich Paul R. advisor. Thesis advisor
Tuljapurkar Shripad