Genetic and cultural adaptations underlie the establishment of dairy pastoralism in the Tibetan Plateau

Domestication and introduction of dairy animals facilitated the permanent human occupation of the Tibetan Plateau. Yet the history of dairy pastoralism in the Tibetan Plateau remains poorly understood. Little is known how Tibetans adapted to milk and dairy products. We integrated archeological evidence and genetic analysis to show the picture that the dairy ruminants, together with dogs, were introduced from West Eurasia into the Tibetan Plateau since ~3,600 years ago. The genetic admixture between the exotic and indigenous dogs enriched the candidate lactase persistence (LP) allele 10974A>G of West Eurasian origin in Tibetan dogs. In vitro experiments demonstrate that -13838G>A functions as a LP allele in Tibetans. Unlike multiple LP alleles presenting selective signatures in West Eurasians and South Asians, the de novo origin of Tibetan-specific LP allele -13838G>A with low frequency (~6-7%) and absence of selection corresponds -13910C>T in pastoralists across eastern Eurasia steppe.Results depict a novel scenario of genetic and cultural adaptations to diet, and expand current understanding of the establishment of dairy pastoralism in the Tibetan Plateau.乳用家畜的驯化与引进，推动了人类永久定居青藏高原（Tibetan Plateau）。然而，青藏高原乳用畜牧的历史仍未得到充分阐释，学界对藏民族如何适应奶类及乳制品的机制尚所知甚少。本研究整合考古证据与遗传分析，揭示了约3600年前起，乳用反刍动物与犬类便从西欧亚大陆（West Eurasia）传入青藏高原的图景。外来犬只与本土犬只的遗传混合，使得源自西欧亚大陆的候选乳糖耐受（lactase persistence, LP）等位基因10974A>G在藏犬中富集。体外实验证实，-13838G>A位点可作为藏族人群的乳糖耐受等位基因。与西欧亚及南亚人群中存在多种带有选择信号的乳糖耐受等位基因不同，藏族特异性乳糖耐受等位基因-13838G>A为新发起源，频率仅约6%-7%，且未受到选择作用，这与欧亚大陆东部草原游牧人群中的-13910C>T位点情况相符。本研究描绘了饮食适应相关遗传与文化适应的全新图景，拓展了学界对青藏高原乳用畜牧体系建立过程的认知。