<펌>(AR33K)Mysterious East Asians vanished during the ice age. This group replaced them. -Live Science

Mysterious East Asians vanished during the ice age. This group replaced them.

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By Laura Geggel

 published June 08, 2021

 

A new group moved into East Asia about 19,000 years ago.

 

The ancestors of today's East Asians moved into the region about 19,000 years ago, and in doing so, they replaced the mysterious people who were living there before them, a new study finds. 

Researchers learned about these mysterious people by comparing the genetics of "Tianyuan man," a 40,000-year-old individual found in Tianyuan Cave in Beijing, with DNA from ancient human remains belonging to 25 individuals from the Amur region, which includes parts of eastern China and Russia. 

 

The team found that Tianyuan man's ancestry was likely widespread from 40,000 years to 33,000 years ago across East Asia. But then, it disappeared and a new population emerged around 19,000 years ago, just as the Last Glacial Maximum (LGM) — when the ice sheets were at their maximum extent from about 26,500 years to 19,000 years ago — was ending, said study senior author Qiaomei Fu, a paleogeneticist at the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences in Beijing. 

 

In 2003, another research group found the remains of Tianyuan man, and to this day the individual's DNA is the earliest known ancient human genome from East Asia. Thanks to Tianyuan man and other archaeological findings, researchers know that modern humans lived in northern East Asia as early as 40,000 years ago. This region includes the Mongolian Plateau, northern China, Japan, the Korean Peninsula and the mountainous regions of the Russian Far East. Recent studies have shed light on the population dynamics of East Asia from about 9,000 years ago to recent historical times, but less is known about what happened from 40,000 to 9,000 years ago, Fu said.

To investigate, Fu and her colleagues compared the DNA of Tianyuan man with the ancient remains of people living in the Amur region, which includes Songnen Plain in northeastern China, between 33,000 and 3,400 years ago. 

 

This stretch of time covers a period when the glaciers that covered vast swaths of the planet receded, "which is crucial to understand what happened to northern East Asians before, during, and after the LGM," Fu told Live Science in an email. After all, northern East Asia falls along similar latitudes as Central and Southern Europe. "In Europe, human population movements and size were influenced by Ice Age climatic fluctuations," the researchers wrote in the study. "These climatic oscillations may have had a similar effect on the population history of high-latitude and high-elevation regions in Asia."

 

The ancient DNA analysis revealed that the oldest person they studied, a Pleistocene female known as AR33K, who lived about 33,000 years ago in the Amur region (AR stands for Amur and 33K stands for 33,000), had the highest genetic similarity with Tianyuan man, compared with all other published ancient and modern individuals from East Asia, Fu said.

 

Another ancient woman, whose DNA was described in a previous study, lived about 34,000 years ago in Salkhit Valley in northeastern Mongolia. This woman was found about 720 miles (1,159 kilometers) from AR33K and about 692 miles (1,114 km) from Tianyuan Cave. A 2020 study in the journal Science found that the Salkhit woman shared 75% of her genetics with Tianyuan man and 25% with another ancient East Asian group that lived along the Yana river in North Siberia. Given that  both AR33K and the Tianyuan man share about 75% of their DNA with the Salkhit woman, it's possible that these people were part of related groups that traveled across East Asia for at least 7,000 years, Fu told Science magazine.

 

Related: 5 ancient languages yet to be deciphered

 

However, unlike the Salkhit woman, AR33K does not have more Yana-related ancestry than Tianyuan man does, the researchers wrote in the new study. "This probably indicates that Tianyuan/AR33K ancestry was widespread before the LGM in northern East Asia, both geographically, from northern China to Mongolia and the Amur region, and temporally, from 40,000 to 33,000 years ago," Fu told Live Science in the email.

 

To explain the Salkhit woman's genetics, perhaps people with Tianyuan-related ancestry paired off with people of Yana-related ancestry in Mongolia, but stayed isolated from ancient people in the Amur region before the LGM, the researchers wrote in the study.

 

 

This map shows how the Salkhit woman (top) has DNA from the Yana in what is now Siberia and Tianyuan man, from what is now China. Around 19,000 years ago (middle red person), a new group of people moved into East Asia. The Amur region (green) has 14,000 years of genetic continuity.  (Image credit: Mao, X. et al. Cell (2021))

 

Oldest "new person"

 

Another standout individual from the study, AR19K, who lived in the Amur region about 19,000 years ago toward the end of the LGM, caught the researchers' attention. AR19K's genetic ancestry is distinct from Tianyuan and AR33K, "indicating a potential population shift," Fu said. In other words, while AR33K and Tianyuan passed on some genes to modern East Asians (Fu called them "basal to all East Asians"), the populations they came from vanished at some point during the LGM. 

 

In fact, AR19K is "the earliest northern East Asian yet identified," meaning this individual is ancestral to ancient northern East Asians. The identification of this northern East Asian ancestor "indicates that north-south genetic separation in East Asia is as early as 19,000 years ago, 10,000 years earlier than previously discovered," Fu said.

 

Some East Asia areas have had remarkable genetic ties to the past, the younger samples revealed. For instance, researchers previously thought that modern populations in the Amur region had an 8,000-year genetic continuity with Neolithic foragers and farmers who lived at Devil's Gate cave in Far Eastern Russia and the Amur region. But the new analyses showed that this continuity goes back 14,000 years, or "6,000 years earlier than previously proposed," Fu said.

 

Hair, sweat and teeth

 

The study also narrowed the time window that an Asian-specific genetic variant, known as EDAR V370A, emerged. This variant is associated with traits such as thicker hair shafts, more sweat glands and shovel-shaped incisors, Fu said.

 

 

"We show that this genetic variant was likely to be elevated to high frequency after the LGM," Fu said. "Our direct observations using ancient DNA likely support the hypothesis that selection on EDAR V370A increased vitamin D in breast milk in a low-UV [ultraviolet light] environment."

Overall, the results suggest the LGM had a profound impact on the ancient people who lived in East Asia. "This ancient DNA study ... offers us a clearer picture of the deep population history of northern East Asia," Fu said.

 

The study was published online May 27 in the journal Cell.

 

Originally published on Live Science.