A newly appointed professor in the Department of Anthropology at UC Santa Barbara, Douglas Kennett, working alongside a multitude of other researchers across many institutions and disciplines, has helped to paint a clearer picture of the human story of ancient migration to South and Central Asia, and the spread of language and practices which coincided with this.

The paper, “The formation of human populations in South and Central Asia,” published in the journal Science, brought together the remains of over 500 ancient humans from Central Asia and Southern Asia. The researchers extracted and sequenced DNA from their remains and compared them genomically with previously sequenced ancient DNA as well as baseline data from contemporary populations in Eurasia.

“The foundation is archaeological, all of the human skeletal material sampled and analyzed from archaeological sites throughout South Asia and Central Asia … to look at sort of the population history of people in the area over the last 8,000 years,” Kennett said.

His lab at Penn State University, where he worked for much of the study, performed radiocarbon dating on individual remains so as to map out the data in the chronological sense.

“It was really an impressive increase in the number of information that we have about populations and particularly in South Asia and Central Asia, which was an area that had not been really focused on too much,” Kennett detailed. “There are definitely periods of time that are better represented than others. But given the size of the dataset, we were able to cover the bases pretty well.”

With this new information came a number of revelations regarding the origin and linguistic spread of Central and Southern Asian people and Indo-European languages in general, lending even more credibility to the steppe theory, which posits that people from the Eurasian region were those who spread the Indo-European language family west into Europe and east into Asia.

This runs in contrast to its prominent counterpart, the Anatolian hypothesis, which claims instead that farmers from what would presently be called Turkey spread Indo-European language both west and east, crossing Europe and simultaneously digging deeper into Southern Asia.

“This research pretty much puts it to rest, the debate which has been going on for 200 years,” Kennett said.

“The Eurasian steppe is where pastoralism developed … independent of what happens in the Near East. Those populations were very successful and then spread out and they were the ones that actually were carrying the European languages. There’s some data from Europe that was published previously that suggests that that was the case. And then this study reinforces that idea.”

More specifically, the research found different periods of migration and the spread of practices which affected the region in different ways.

About 8,000 years ago, there was an early spread of farmers who developed an agricultural economy which spread into Europe and Central Asia, but not South Asia, according to Kennett.

“Then later on, starting about 4,000 years ago you have a development of a sort of pastoral economy that’s very animal-focused and that’s in that steppe region. So with the European languages, that’s the linkage of South Asia which is consistent with the idea that ties the European languages to this later spread of pastoral peoples,” Kennett said.

The authors’ depiction of the spread of Yamnaya Steppe pastoralist ancestry from a focal point found north of the Black Sea into Europe and South Asia during the Bronze Age is shown. Pie charts represent the proportion of Yamnaya ancestry. / Courtesy of Douglas Kennett

Among Kennett’s primary collaborators was David Reich, whose lab at Harvard University was tasked with extracting DNA from the skeletal material of individuals.

“He’s done large scale studies all over the world. I’ve been working with him for the last three years or so helping him with the chronological dimensions,” Kennett stated.

While mapping the spread of people chronologically through radiocarbon dating, Kennett and his research group also simultaneously looked for certain properties which served as markers of diet, which could provide indications regarding what sort of lifestyle was being practiced by the individual.

Pastoral economies, agricultural economies and hunter-gatherer economies all would have slightly different markers, for instance.

“There’s that old adage that ‘you are what you eat.’ If people are eating a lot of specific foods, if they’re eating a lot of meat, that will show up in their nitrogen isotopes. They look distinctive isotopically. Then we can compare the date of the individual, the DNA, like where they are, what their ancestry is and then also look at the diet,” Kennett described.

Kennett plans to continue working with these isotopic analyses in a subsequent study in order to better understand the diets of ancient people with regards to agriculture, pastoralism and other comparative lifestyles.

“I’m an environmental archaeologist. One of the things that I’m interested in more generally is the environmental impacts that agricultural and pastoral populations had on the landscape which we can then explore with isotopic analyses or other kinds of archaeological and ecological studies,” Kennett said.

Speaking on the paper published in Science, Kennett believes that the most illuminating ramifications are the “big picture” ones, which speak to how agricultural and pastoral populations emerge and expand, “and then what that means ultimately for the formation of later, more complex societies.”

“That’s kind of the global story as humans, anyways.”

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