Fine‐scale north‐to‐south genetic admixture profile in Shaanxi Han Chinese revealed by genome‐wide demographic history reconstruction

The Han Chinese are the world's largest ethnic group residing across China. Shaanxi province in northern China was a pastoral–agricultural interlacing region sensitive to climate change since Neolithic times, which makes it a vital place for studying population dynamics. However, genetic studies of Shaanxi Han are underrepresented due to the lack of high‐density sampling and genome‐wide data. Here, we genotyped 700 000 single nucleotide polymorphisms (SNPs) in 200 Han individuals from nine populations in Shaanxi and compared with available modern and ancient Eurasian individuals. We revealed a north–south genetic cline in Han Chinese with Shaanxi Han locating at the northern side of the cline. We detected the western Eurasian‐related admixture in Shaanxi populations, especially in Guanzhong and Shanbei Han Chinese in proportions of 2%–4.6%. Shaanxi Han were suggested to derive a large part of ancestry (39%–69%) from a lineage that also contributed largely to ancient and present‐day Tibetans (85%) as well as southern Han, supporting the common northern China origin of modern Sino‐Tibetan‐speaking populations and southwestward expansion of millet farmers from the middle‐upper Yellow River Basin to the Tibetan Plateau and to southern China. The rest of the ancestry of Shaanxi Han was from a lineage closely related to ancient and present‐day Austronesian and Tai‐Kadai speaking populations in southern China and Southeast Asia. We also observed a genetic substructure in Shaanxi Han in terms of north–south‐related ancestry corresponding well to the latitudes. Maternal mitochondrial DNA and paternal Y‐chromosome lineages further demonstrated the aforementioned admixture pattern of Han Chinese in Shaanxi province.