Genetic evidence on the deep history of human populations

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Recent research has shown that modern humans carry DNA derived from archaic hominin populations, such as Neanderthals and Denisovans, in the distant past. This project will use genetic data, together with a newly-developed statistical method, to study the history of humans and their close relatives during the past two million years. The results will inform us about the speed with which populations become reproductively isolated after separation. The methods will be of interest to conservation biologists, who must estimate rates of interbreeding in order to decide whether a species deserves protected status. The results also will be useful to medical researchers who must control for the effects of history as they study the causes of genetic disease. The project will support graduate training, as well as a workshop that will train geneticists from throughout the US in methods of bioinformatics and computational genetics and support efforts to broaden participation in STEM research.Modern humans carry genetic signatures of past admixture with Neanderthals and Denisovans. Research has also documented episodes of very small population size, during which natural selection was ineffective, and harmful mutations were able to accumulate. Our understanding of these events is incomplete however, because of limitations in the statistical methods used. The current project will use a new method, which corrects these problems and allows us to see farther into the past. It will (1) estimate the fraction of Denisovan DNA in several human populations of Asia and Oceania; (2) study interbreeding between modern humans and “superarchaics,” who separated from other hominins early in the history of the genus Homo; and (3) test the hypothesis that Middle Eastern populations received gene flow from a hypothetical population of “basal Eurasians,” which separated from other Eurasians before the separation of Europeans from East Asians.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.