Genetic diversity of two Neolithic populations provides evidence of farming expansions in North China.

The West Liao River Valley and the Yellow River Valley are recognized Neolithic farming centers in North China. The population dynamics between these two centers have significantly contributed to the present-day genetic patterns and the agricultural advances of North China. To understand the Neolithic farming expansions between the West Liao River Valley and the Yellow River Valley, we analyzed mitochondrial DNA (mtDNA) and the Y chromosome of 48 individuals from two archeological sites, Jiangjialiang (>3000 BC) and Sanguan (~1500 BC). These two sites are situated between the two farming centers and experienced a subsistence shift from hunting to farming. We did not find a significant difference in the mtDNA, but their genetic variations in the Y chromosome were different. Individuals from the Jiangjialiang belonged to two Y haplogroups, N1 (not N1a or N1c) and N1c. The individuals from the Sanguan are Y haplogroup O3. Two stages of migration are supported. Populations from the West Liao River Valley spread south at about 3000 BC, and a second northward expansion from the Yellow River Valley occurred later (3000-1500 BC).