. "12 Gene–Culture Coevolution in the Age of Genomics--Peter J. Richerson, Robert Boyd, and Joseph Henrich ." In the Light of Evolution IV: The Human Condition. Washington, DC: The National Academies Press, 2010.
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In the Light of Evolution Volume IV: The Human Condition
As mentioned in the earlier, genomic studies have already revolutionized our understanding of our migration out of Africa, following the pioneering mitochondrial DNA phylogeny of Cann, Stoneking, and Wilson (1987). By now it is clear that much of the genetic variation and genetic diversity in human populations is consistent with a spread out of Africa about 60–50 kya (Ramachandran et al., 2005; Liu et al., 2006). Examples of genes that very likely came under selection in this period include genes affecting skin pigmentation (McEvoy et al., 2006; Myles et al., 2007). As with genes selected in the Holocene, different populations have reached parallel solutions to the same adaptive problem. The genes that underlie the light skin adaptation to increase vitamin D photosynthesis in cold, low-sunlight environments are different in eastern and western Eurasia (Jablonski and Chaplin, Chapter 9, this volume).
Ideally, genomic data will provide an accurate timescale for major evolutionary events, which can then be used in conjunction with paleoanthropological data to resolve some of the puzzles noted above. This quest for well-dated selection events will require more data and improved methods. The best tool for younger events, dates estimated from the long haplotypes associated with genes under selection, is nearly erased by recombination in this earlier period. The reduced diversity and excess of rare haplotypes in the regions flanking genes under selection in theory will lead to datable genomic events in this time period (Sabeti et al., 2006). An interesting example of another kind of data that might prove useful is the study of the evolution of human commensals and parasites. For example, the human body louse lives in clothing but feeds on the body. It evolved from the head louse, which lives in hair, 72 kya ± 42 kya (Kittler et al., 2003). Thus, clothing must have evolved fairly recently, perhaps associated with the out-of-Africa migration of anatomically modern humans to higher latitudes. Aside from the human genome itself, we wonder how much evolutionary history might be reconstructed from the diverse microflora that inhabit our digestive tract and skin (Hattori and Taylor, 2009).
Complete sequences of Neandertal autosomal DNA promise to revolutionize our understanding of selection in the Late Pleistocene (Green et al., 2006). Improvements in the database of fossil mitochondrial DNA sequences also promise much (Krause et al., 2010). Assuming that the ancestral Homo heidelbergensis population that gave rise to Neandertals and ourselves lived around 200–600 kya (Weaver et al., 2008), and if there was no introgression of genes from Neandertals to anatomically modern humans (or that such introgression as did occur is detectable), then any genetic variants that we share with Neandertals (such as, possibly, the derived FOXP2 variant) must have had its origin before the date of separation of the two species. Derived genes not shared with Neandertals are candidates to have evolved on the anatomically modern lineage. We might