Using ancient DNA studies to solve mysteries of East Asia’s Population
In brief: DNA sequencing studies are helping to show in greater detail how early humans populated China, other parts of east Asia, and the Mariana Islands.
Sparse sampling and a lack of ancient DNA means that the so-called “deep population history” of east Asia is poorly understood and makes people ask, “where did they come from?”.
“Deep” prehistory in human terms generally refers to the early Holocene, or roughly 10,000 BC, though DNA sequencing studies are delving even deeper than that, unearthing fascinating details about Paleolithic human populations, when the entire human population may have totaled less than 10,000.
Three recent studies focusing on the formation of human populations in east Asia and the Pacific have illuminated previously dark corners of history: a gene flow study published in Nature, an Ancient DNA study presented at the 5th Marianas History Conference, and another Ancient DNA study published in PNAS.
Asian Gene flow studies in Mongolia and China
A recent study published in Nature investigated genome-wide data from 166 east Asians dating to 6000 BCE to 1000 CE and 46 present-day groups. The study of these groups is important not just because little is known about their ancestry but because this region was one of the earliest centers of animal and plant domestication, and today is home to an incredible diversity of language families.
Only two pre-Ice Age genomes are available from the region: a 40,000-year-old individual found in Tianyuan Cave in northern China and a 35,000-year-old Salkhit individual from Mongolia. Study of post-Ice Age genomes is being used to determine whether east Asia was settled via coastal or interior routes. Genetic evidence has shown that Tibetans have haplogroup ties to modern Japanese, ancient Jomon Japanese hunter-gatherers, and indigenous Andaman Islanders. Included in those ties are haplogroup M10 and haplogroup M12.
Results of the study suggest that human movement into east Asia likely occurred both from the coast and the interior.
“Indigenous Andaman islanders of the Bay of Bengal, Indigenous Tibetans, ancient Taiwanese, and ancient and modern Japanese all derive ancestry from a deep shared lineage that split from other East Asian lineages more than 40,000 years ago,” David Reich, co-senior author of the study and a professor of genetics and human evolutionary biology at Harvard University, told Science Daily.
The coastal route linked Southeast Asia, Japan, and coastal China, while the finding from the Tianyuan Cave links together evidence of settlement from the Amur River Basin and early farmers in the West Liao and Yellow River regions. Last year, a study found links between Siberians and early Americans, but failed to answer questions about how and where they traveled.
Ancient DNA provides more detail of Marianas Islands migration
A separate study, meanwhile, has shown evidence of migration patterns in the Mariana Islands.
The Mariana Islands is a group of mostly dormant volcanic islands in the western Pacific north of New Guinea and east of the Philippines. Today, most of the islands are part of Guam and the Northern Mariana Islands.
The indigenous inhabitants of the islands are the Chamorro, or CHamoru. Researchers in 2013 reported findings indicating that the first settlers of the Mariana Islands arrived there after making what was thought to the longest uninterrupted ocean voyage in human history and that the island of Tinian was the first to have been settled. Such epic sea journeys have been cited before in ancient DNA studies.
Excavations of burial sites and subsequent DNA studies found two waves of settlement: one from the Southeast Asian Bronze Age, where marine foragers visited the islands seeking resources, and another from the Southeast Asian Iron Age, where fishers and farmers permanently occupied the region. Later arrivals have a larger quantity and variety of grave goods, and there were changes in diet or food processing.
Both groups have the same deep East Asian ancestry, though later arrivals likely came from Sulawesi, a large island in Indonesia, and there is no direct prehistoric connection to the Philippines.
When did anatomically modern humans first appear in southern China?
The occasional finding of anatomically modern humans in caves in southern China has at times challenged the theory that all humans migrated out of Africa 65,000 to 45,000 years ago.
Those findings in the Huanglong, Zhiren, Luna, and Fuyan caves in southern China have suggested one or more prior dispersals to the long-established Out of Africa dispersal, perhaps as early as 120,000 years ago.
A recent study, however, has quashed that theory by more precisely dating those cave findings and supporting earlier genetic studies that the first appearance of anatomically modern humans in the region was 50,000 to 45,000 years ago.
The reason for the discrepancies? Genetic evidence from the subtropical caves is incredibly difficult to analyze. That was the similar answer after investigations into findings in Mexico.
“Our work highlights the surprisingly complex depositional history recorded at these subtropical caves which involved one or more episodes of erosion and redeposition or intrusion as recently as the late Holocene,” the investigators wrote. “In light of our findings, we conclude that claims for an early arrival of anatomically modern humans in southern China as seemingly documented at Huanglong, Luna, and Fuyan caves cannot be substantiated at present.”
