Effect of Archaic Admixture on Modern Human Adaptations

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Recent genetic studies indicate that modern humans interbred with archaic hominin species such as Neanderthals and Denisovans in the past. Some of the archaic genes found in modern humans appear to play important roles in immunity and in adaptations involving skin and hair, but our understanding of the contributions and effects of archaic genes is still incomplete. This project will study the effects on modern humans of DNA derived from ancient interbreeding, telling us how much archaic DNA is in modern humans and how this DNA affects body fat. The investigator will develop and make freely available statistical tools for the study of interbreeding and adaptive evolution. These tools will address current analytical biases that limit our understanding of archaic genes in humans, and will be useful in other fields of study, like conservation biology, where there is a need to define and distinguish among species. The project will support training of a graduate student in human evolutionary genetics, dissemination of findings as part of an undergraduate textbook on evolution, and K-12 and public outreach through frequent lectures on human evolution to local school and community groups. Our current understanding of archaic admixture is compromised by pervasive statistical biases. Given that archaic alleles are known to influence modern human adaptive phenotypes at several genetic loci, it is important that these biases be addressed. To correct this problem, this project will develop a new statistical method to estimate gene flow among multiple populations using genomic data. The method will make it possible to estimate levels of archaic DNA in modern human populations, sizes and separation times of ancestral populations, and effects of archaic DNA on polygenic characters such as stature, blood pressure, or body weight. The project will apply this method to a study of fat storage in modern humans, testing the hypothesis that we have inherited from Neanderthals a tendency to store fat - a relic of their adaptation to seasonal food shortages in Pleistocene Europe.