Bronze Age population dynamics and the rise of dairy pastoralism on the eastern Eurasian steppe

Recent paleogenomic studies have shown that migrations of Western steppeherders (WSH) beginning in the Eneolithic (ca. 3300–2700 BCE) profoundly transformed the genes and culturesof Europeand central Asia. Compared with Europe, however, the eastern extent of this WSH expansion is not well defined. Here we present genomic and proteomic data from 22 directly dated Late Bronze Ageburials putatively associated with early pastoralismin northern Mongolia (ca. 1380–975 BCE). Genome-wide analysis reveals that they are largely descended from a population represented by Early Bronze Age hunter-gatherersin the Baikal region, with only a limited contribution (∼7%) of WSH ancestry. At the same time, however, mass spectrometry analysis of dental calculus provides direct protein evidence of bovine, sheep, and goat milk consumption in seven of nine individuals. No individuals showed molecular evidence of lactase persistence, and only one individual exhibited evidence of >10% WSH ancestry, despite the presence of WSH populations in the nearby Altai-Sayan region for more than a millennium. Unlike the spread of Neolithic farming in Europe and the expansion of Bronze Age pastoralismon the Western steppe, our results indicate that ruminant dairy pastoralismwas adopted on the Eastern steppeby local hunter-gatherersthrough a process of cultural transmission and minimal genetic exchangewith outside groups.