NEW YORK – By analyzing genetic data from ancient and present-day East Asians, researchers have begun to piece together the region's deep population history.
The genetic diversity and population history of East Asia, which was a site of early plant and animal domestication, is not well understood, in part due to limited sampling of present-day individuals and a lack of ancient DNA samples.
Combining genetic data from 166 ancient East Asians and 46 present-day groups, an international team of researchers has now begun to test theories of how East Asian populations formed. As they reported on Monday in Nature, the researchers found early East Asian ancestry derives from a coastal expansion, but also from interior routes. They additionally examined relationships between the spread of ancestry and languages.
"With high-resolution modern and ancient data, we can connect the dots between ancient and modern East Asians," co-first author Chuan-Chao Wang, director of the Institute of Anthropology at Xiamen University in China, said in a statement.
The researchers analyzed DNA collected from 383 modern-day individuals belonging to 46 populations from China and Nepal. At the same time, they generated genetic data for samples from 166 ancient individuals who lived throughout East Asia between about 8,000 years ago and 1,000 years ago. They further folded previously published data from 1,079 ancient individuals and 3,265 present-day individuals into their analyses.
The early peopling of East Asia has been a source of debate, the researchers noted. Some scientists have suggested a coastal expansion and others an interior one. Through their modeling, Wang and colleagues found that much of East Asia ancestry can be considered to be a mixture of two ancient populations: an group related to the 40,000-year-old Tianyuan Cave individual — one of the two pre-Ice Age individuals found in East Asia — and a lineage related to Indigenous Andaman Islanders, the Onge.
The Onge contribution, the researchers noted, is more concentrated among coastal populations, while the Tianyuan-related ancestry is found more in the interior, indicating the peopling of East Asia may have followed both coastal and interior routes.
The researchers also investigated whether farming and languages spread together in East Asia. In particular, they focused on the Transeurasian hypothesis that suggests that Mongolic, Turkic, Tungusic, Koreanic, and Japonic language families descended from proto-language linked to the expansion of millet farmers from near the West Liao River in northeastern China west to Mongolia, north toward Siberia, and east toward Korea and Japan.
In their analysis, they found that present-day populations speaking these languages have some shared genetic ancestry linked to the Tianyuan lineage, but that Mongolic, Turkic, and Tungusic speakers do not appear to harbor a signature of West Liao River farmer ancestry. However, Korean and Japanese populations do appear to have West Liao River farmer ancestry.
At the same time, the researchers noted that Tibetans and Han Chinese — Sino-Tibetan language speakers — have ancestry linked to a population closely related to Yellow River farmers, and underscored genetic ties linked to the spread of rice farming in East Asia and Southeast Asia.
Mongolia, the researchers reported, has served as a region of admixture between west and east Eurasians. In their analysis, they found four sources of ancestry: East Mongolian hunter-gatherers from 6,000 to 5,000 BC; Neolithic hunter-gatherers from 5,700 BC to 5,400 BC; ancestry linked to the Afanasievo culture, which is related to the Yamnaya steppe pastoralists from about 3,000 BC; and ancestry similar to that of the Sintashta culture that is about two-thirds Yamnaya and one-third European farmers from about 1,400 BC.
"This increases the plausibility of the theory that the Yamnaya expansion was a vector of spread, not only of the ancestors of all spoken Indo-European languages, but also of the early- branching Tocharian languages attested from written records in Iron Age western China," co-senior author Johannes Krause, a director at the Max Planck Institute for Evolutionary Anthropology, said in a statement.