Linguistic, archaeological and genetic evidence suggests multiple agriculture-driven migrations of Sino-Tibetan speakers from Northern China to the Indian subcontinent

The spread of language families is hypothesized to have occurred via agricultural and demographic transitions that drove populations outwards from agricultural centres of origin, “demic diffusion”. However, the geographical origins of language families are often tied to where greatest linguistic diversity is seen. For the Sino-Tibetan language family this creates a conflict, as maximal linguistic diversity lies in North-Eastern India and Nepal, whereas centres of Neolithic crop domestication in the Yellow and Yangtze River Basins have low linguistic diversity today. Therefore either Sino-Tibetan languages originated in North-Eastern India, and spread by means other than demic diffusion; or multiple diffusions of agriculturalists occurred from a once linguistically diverse homeland, in which linguistic diversity was maintained or increased as peoples spread westwards, but was lost in the homeland.

To explore these two hypotheses, using evidence from linguistics, archaeology and genetics, we compiled existing data on Chinese millets, cultivated trees, and agricultural tools (harvesting knives, shouldered spades) alongside data for wheat and barley from Western Eurasia. These elements were explored alongside existing information from genetic studies and for West Asian animal domesticates.

We differentiate a northern cultural and southern demic diffusion for various elements originating in East Asia. In Central Asia a small number of eastern Eurasian elements (millets by 2500 BC, spades by 1st millennium BC) spread west through pre-existing agricultural populations by cultural-diffusion, but significantly did not include language families nor genetic lineages. The southern dispersal driven by demic diffusion of millet farmers carried a more expansive range of eastern cultural elements; millets, spades, hairpins, harvesting knives, house plans, and significantly languages and genetic lineages. We hypothesize a period of demic diffusion beginning c.2500-2000 BC from the southeastern Plateau through Eastern Tibet and the Himalayan foothills, brought peoples, languages and Eastern Eurasian cultural elements eventually to the Kashmir region. We conclude two routes, the Sichuan–Tibet–Kashmir and Yunnan–Assam ones, are the most plausible pathways linking Northern China and Northern India during this period.