Evidence of Local Adaptation to Climate and Diet in Siberians
One of the greatest challenges modern humans faced as the migrated into Eurasia was a cold climate. This was especially true of Siberia, where mean January temperatures of -40° C are not uncommon and temperatures of -70° C have been recorded. Humans adapted to this environment in multiple ways, but the role of genetic adaptation has been unclear. In my dissertation, I addressed this question with large-scale genomic data, and statistical and informatics-based methods designed to find “signals of selection”. In this defense, I will first discuss the motivating theory and methods behind my approach. I will then present evidence of positive natural selection acting on missense variants in three genes, PLA2G2A, PLIN1 and ANGPTL8, all with essential functions in lipid metabolism and brown adipose tissue function. In addition, I will provide strong empirical support for the adaptive introgression of a small region on chromosome 1 from a Denisovan-like archaic hominid into modern humans. I will conclude with a discussion of the nature of adaptation in Siberians, the limitations of current approaches, and ideas for future work.