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

Recent paleogenomic studies have shown that migrations of Western steppe herders (WSH) beginning in the Eneolithic (ca. 3300-2700 BCE) profoundly transformed the genes and cultures of Europe and 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 Age burials putatively associated with early pastoralism in northern Mongolia (ca. 1380-975 BCE). Genome-wide analysis reveals that they are largely descended from a population represented by Early Bronze Age hunter-gatherers in 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 pastoralism on the Western steppe, our results indicate that ruminant dairy pastoralism was adopted on the Eastern steppe by local hunter-gatherers through a process of cultural transmission and minimal genetic exchange with outside groups.

近期的古基因组学研究表明，始于铜石并用时代（约公元前3300-2700年）的西草原牧民（Western steppe herders, WSH）迁徙，深刻重塑了欧洲与中亚的基因与文化面貌。然而与欧洲地区相比，学界对该WSH扩张事件的东部边界尚未形成清晰认知。本研究报道了蒙古国北部（约公元前1380-975年）22例经直接定年的青铜时代晚期墓葬的基因组与蛋白质组数据，这些墓葬据信与早期畜牧活动相关。全基因组分析显示，这些个体主要源自贝加尔湖地区青铜时代早期的狩猎采集人群，仅携带约7%的WSH祖源成分。与此同时，对牙结石的质谱分析结果显示，9例个体中有7例存在食用牛、绵羊与山羊乳的直接蛋白质证据。尽管周边的阿尔泰-萨彦地区已存在WSH种群长达千余年，但所有个体均未检出乳糖酶持久性的分子标记，且仅1例个体的WSH祖源占比超过10%。与欧洲新石器时代农业传播以及西草原青铜时代畜牧扩张的模式不同，本研究结果表明，东草原地区的反刍乳制品畜牧是由当地狩猎采集人群通过文化传播、并与外部群体发生极少量基因交流的方式所接纳的。