Department of Anthropology, University of Wisconsin-Madison
April 14, 2016 3:45, Imperial Ballroom B
Ancient DNA information has profoundly shifted our understanding of the movements and interactions of prehistoric peoples. Until recently, it was widely assumed that except for the largest-scale cultural changes, such as the initial advent of farming or appearance of Upper Paleolithic hunting technology, most of human prehistory was dominated by in situ evolution with isolation-by-distance. Now, however, it is clear that regional to continental-scale genetic turnover was a frequent phenomenon in prehistoric human populations. The mechanisms and dynamics of such genetic turnovers are not well explained by traditional models of human migration and population mixture, as derived from the ethnographic record of hunter-gatherers and other small-scale societies. Here, I explore a spectrum of complex systems models to understand how small-scale societies in the past may have repeatedly exploded across large geographic areas. By examining the interaction of demography, selection, and culture, it appears that the migration and mixture among populations on a generational scale give rise to self-organized criticality on a millennial scale, often causing substantial redistribution of genetic variation across large geographic regions. This dynamic is consistent with evidence from ancient DNA, and brings a new perspective on the existence, coherence and disappearance of Pleistocene human groups like the Neandertals and Denisovans. In particular, the pattern of ancient population structure and subsequent introgression of ancient alleles may an outcome of these complex dynamics of cultural population systems in the face of human population growth.
Work was supported by the Wisconsin Alumni Research Foundation