Sunday, June 20, 2021

Population Dynamics and the Formation of the Central Asian Empires

In a new study published in the journal Cell, an international research team has investigated the genetic, sociopolitical, and cultural changes that accompanied the emergence of the Central Asian empires. The team analyzed genome-wide data from 214 East Eurasian individuals spanning six millennia and discussed the changes in population and material culture that preceded the rise of the nomadic empires of the Xiongnu and Mongols.

From the late Bronze Age to the Middle Ages, the Eastern Eurasian steppe was home to a number of very influential nomadic empires. The realm of the Xiongnu (209 B.C. to A.D. 98) and the Mongolian empires (916-1125) left deep marks in the demography and geopolitics of Eurasia. Due to a lack of large-scale genetic studies, the origins, interactions, and relationships of the people who formed these states remained largely unknown.

Deer stone with carvings built in the Mongolian Bronze Age. (Image: William Taylor)
Deer stone with carvings built in the Mongolian Bronze Age. (Image: William Taylor)

In order to understand the population dynamics that helped the steppe-rich to rise, researchers from the Max Planck Institute for the History of Man (MPI-SHH), the National University of Mongolia, and partner institutions in Mongolia, Russia, Korea, and the USA collected and analyzed genome data from 214 individuals.

The samples come from 85 Mongolian and three Russian archaeological sites, and their age is between around 8,400 years and 1,400 years. This makes this study one of the largest studies of ancient East and Inner Asian DNA to date.

Present-day home in the Mongolian countryside, known as a ger (Mongolian) or yurt (Russian). (Credit: Christina Warinner)
Present-day home in the Mongolian countryside, known as a ger (Mongolian) or yurt (Russian). (Image: Christina Warinner)

During the Middle Holocene, the Eurasian steppe was settled by hunters and gatherers of Northeast Asian (ANA) and North Eurasian (ANE) descent. About 5000 years ago, the spread of the Afanasievo culture from the Altai Mountains brought dairy farming to the region, whose origins can be traced back to the Yamnaya steppe herders from the Black Sea region more than 3000 km to the west.

The cultural impact of this migration was enormous, although it left only marginal genetic traces: in the Middle to Late Bronze Age, dairy farming was widespread among the population groups throughout the eastern steppe.

Abrupt mixing of long-separated gene pools and influx of new lineages in the central Asian empires

In the late Bronze Age and early Iron Age, the populations of western, northern, southern, and central Mongolia formed three different, geographically structured gene pools. These gene pools remained separate from one another for more than a millennium until increased mobility, likely promoted by the advent of horse riding, disintegrated these structures.

A horse-hair banner adorns a hillside monument in central Bayankhongor province, Mongolia. (Credit: William Taylor)
A horse-hair banner adorns a hillside monument in central Bayankhongor Province, Mongolia. (Image: William Taylor)

The emergence of the Xiongnu Empire, in the north of central Mongolia, the first nomadic empire in Asia, occurred at the same time as this population mix and the influx of new genetic ancestry from all over Eurasia, from the Black Sea to China. Dr. Choongwon Jeong, lead author of the study and professor of biology at Seoul National University, said:

“Instead of a mere genetic upheaval or replacement, the rise of the Xiongnu is closely linked to an abrupt mixing of populations that were previously separated for millennia. As a result, the Mongolian Xiongnu show an impressive genetic diversity, which reflects a large part of the genetic diversity of Eurasia.”

A thousand years later, individuals from the Mongolian Empire, one of the largest contiguous empires in history, showed a marked increase in Eastern Eurasian ancestry compared to individuals from the earlier Xiongnu, Turkish, and Uyghur periods. This increase was accompanied by an almost complete loss of the old ANE parentage.

Today’s dairy herders have traditions that go back thousands of years to Mongolia’s prehistory. (Image: Christina Warinner)

By the fall of the Mongol Empire, the genetic makeup of the eastern steppe had changed dramatically and finally stabilized in the genetic profile that characterizes the Mongols of today. Ke Wang, co-first author of the study and Ph.D. student at MPI-SHH, said:

“Our study reveals not only an early genetic contribution from populations of the western steppe, but also a marked increase in Eastern Eurasian ancestry during the time of the Mongol Empire. The genetic history of the region is remarkably dynamic and the analysis of ancient DNA gradually reveals the complexity of the population events that have shaped the Eurasian steppe.”

Lack of lactase persistence despite 5,000 years of dairy farming

In addition to the effects of these genetic events on political structures, the research team also examined the relationship between genetics and economic form. Despite more than 5,000 years of dairy farming in the region, which still makes an important contribution to the diet in Mongolia, no evidence of lactase persistence, a genetic trait that enables lactose to be digested, could be found. Senior author Dr. Christina Warinner, Professor of Anthropology at Harvard University and Research Group Leader at MPI-SHH, said:

“The fact that we were unable to detect lactase persistence in either the present or the then population calls into question current medical assumptions regarding lactose intolerance and suggests a much more complicated history of the dairy industry. In our further research we turn to the intestinal flora to understand how populations adapted to a milk-based diet.”

Dr. Erdene Myagmar, co-senior author of the study and professor of anthropology and archaeology at the National University of Mongolia, concludes:

“The reconstruction of 6,000 years of Mongolia’s genetic history has had a lasting impact on our understanding of the archaeology of this region. While we managed to answer some long-standing questions, the study also raised new questions and had some surprises in store. We hope that this study will stimulate further research that will help uncover the diverse and complex relationships between ancestry, culture, technology and politics during the rise of the nomadic empires of Asia.”

Provided by: Max Planck Society  [Note: Materials may be edited for content and length.]

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Troy Oakes
Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.

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