Razib Khan One-stop-shopping for all of my content

March 1, 2010

The cultural animal as an evolving animal

Filed under: Biocultural,Culture,Evolution,Genetics,Human Evolution — Razib @ 4:41 pm

Nicholas Wade has an article in The New York Times, Human Culture, an Evolutionary Force. One point to highlight:

By this criterion, many of the genes under selection seem to be responding to conventional pressures. Some are involved in the immune system, and presumably became more common because of the protection they provided against disease. Genes that cause paler skin in Europeans or Asians are probably a response to geography and climate.

But even in this case these non-cultural targets of selection have an ultimate cultural cause. The Eurasian pathogen environment is strongly shaped by the fact that humans have lived at high densities under nutritional stress for thousands of years. The uniqueness of the Eurasian adaptations are evident whenever these populations encounter hunter-gatherers. Adaptation to malaria is something which most biologists accept as a clear case of natural selection, but malaria has become ubiquitous only within the past 5-10,000 years in many regions because of ecological changes wrought by humans as they shifted their culture (clearing land for agriculture).

More distantly, even if you assume that light skin evolved due to the need to synthesize endogenous vitamin D at high latitudes, what were H. sapiens doing at very high latitudes anyhow? The push into Siberia within the past 30,000 years seems to have been a function of behavioral modernity, contingent upon cultural changes, which themselves may have been contingent upon biological endowments.

It’s a pretty tangled ball. But as a genuine takeaway I have begun to wonder whether the protean nature of human culture, and its relevance for changes in gene frequency, imply that models which posit adaptation driving genetic architectures toward equilibria may not be particularly helpful. In other words, the adaptive landscape may be too volatile for gene frequencies to ever attain a stable fitness peak.


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