Evolution of cumulative culture for niche construction.

A mathematical model of the joint evolution of learning and niche construction in a spatially subdivided population is described, in which culture is used to practice niche construction and can evolve by accumulating small improvements over generations. Individuals allocate their lifetimes to social learning, individual learning, niche construction to improve the environment, and exploitation of resources according to their genetically determined strategies. The coordinated optimal strategy (COS) is defined as the allocation strategy which maximizes the equilibrium fecundity of the population, as opposed to the convergence stable strategy (CSS), which is the strategy favored by natural selection. Both the COS and CSS are analytically derived and compared. It turns out that, although the levels of the CSS in terms of culture and the environmental quality can be high in a highly viscous population, they are in general much lower than those of the COS. It is argued that the discrepancy between the CSS and COS stems from the producer-scrounger structure inherent in the model. Analysis of transient dynamics reveals that the level of culture and the environmental quality may temporarily undergo drastic increases after sudden changes in parameter values, although they eventually drop down to low values due to the genetic adaptation of the time allocation strategy to the new cultural and environmental backgrounds. Implications of the results for human evolution are discussed.