The northeastern regions of Siberia and the North American Arctic are some of the last regions of the world to be inhabited by humans; there, sophisticated technologies were developed for hunting marine mammals. Continued migration waves of ancient Western Eurasians and ancient East Asians into northeastern Siberia led to the early formation of the “Palaeo-Siberians'' in the Late Pleistocene and the “Neo-Siberians'' in the Holocene, the latter being genetically continuous with present-day groups in the region. The North American Arctic was populated by two genetically distinct, archaeologically-defined cultural traditions of Neo-Siberian-related peoples: the Palaeo-Inuit (entering ~5.5 thousand years ago) and the Neo-Inuit (entering ~1 thousand years ago). Limited archaeological and palaeogenomic findings into prehistoric contacts and admixture between ancient Siberian and Arctic groups leave a knowledge gap in the demographic histories of these regions. This thesis comprises palaeogenomic, radiocarbon, and stable carbon and nitrogen isotope datasets of unmatched quality and scale, generated from 217 sets of human remains from northeastern Siberia and North America to investigate population histories, evidence of adaptations to the Arctic environment, and pathogen incidence.

Using allele-frequency based methods, the population genetics analyses in this thesis investigate three main research questions pertaining to Palaeo-Siberian, Palaeo-Inuit, and Neo-Inuit groups. Genetic similarity within and between these groups was determined, adding insight into ancient migrations and population interactions. Adaptations associated with fat metabolism and cold were examined in the ancient Arctic and sub-Arctic groups, at genetic loci that have been proposed to be under selection in present-day populations from the region. Ancient pathogens were identified from the sequencing data of the ancient individuals, expanding the catalogue of human pathogens in these regions over time.

The findings from this thesis elucidate the population histories of Arctic and sub-Arctic groups over time. Importantly, through continued community engagement and knowledge exchange with Indigenous peoples, this interdisciplinary project tells a more complete history of the peopling of the Siberian and North American Arctic.