DNA from this 40,000-year-old jawbone found in China’s Tianyuan Cave supports the presence of multiple populations of modern humans in ancient East Asia.
Shaoguang Zhang/Institute of Vertebrate Paleontology and Paleoanthropology
Some of the first modern humans to settle in East Asia more than 40,000 years ago ranged across the vast northern China Plateau for thousands of years, where they hunted red deer and may have encountered Neanderthals and other archaic humans. But sometime before the end of the last ice age, they vanished. By 19,000 years ago, the landscape was populated by another group of modern humans—the hunter-gatherers who were the ancestors of today’s East Asians, a new study of ancient genomes reveals. That group replaced the early modern humans in northern East Asia, the researchers suggest.
This population turnover in ice age East Asia eerily echoes what happened around the same time in Europe. There, the first modern humans arrived 45,000 years ago, only to be replaced by other groups of hunter-gatherers 19,000 to 14,000 years ago at the end of the Last Glacial Maximum (LGM). “It’s exciting to see some real parallels in Europe and Asia,” says population geneticist David Reich of Harvard Medical School, who was not part of the new study. “There’s enough genomes now to show that there were real population replacements in East Asia, as well as Europe.”
The new study started with an ancient mystery. DNA from a male jawbone in Tianyuan Cave near Beijing proved that modern humans arrived in East Asia some 40,000 years ago. They were still there 34,000 years ago, according to DNA from a female skullcap found in Mongolia’s Salkhit Valley. But after that, their trail went cold: From 34,000 to 9000 years ago, the fossil record has a massive gap across the China Plateau, which extends from Mongolia to northern China and eastern Russia. By 12,000 years ago, newer styles of stone toolkits and pottery appeared in the region, but archaeologists debated who had made them—new migrants or the descendants of the earlier group. “There were definitely modern humans living in East Asia 40,000 years ago, but who knows what happened to them?” says paleogeneticist Qiaomei Fu of the Chinese Academy of Sciences.
So, she and a team of Chinese researchers extracted ancient DNA from the bone fragments of 25 individuals recovered from construction sites in Russia’s Amur region, on the eastern edge of the China Plateau. Direct radiocarbon dating of the bone fragments revealed these individuals lived from 34,000 to 3400 years ago. The oldest, a female who lived between 34,000 and 32,000 years ago, was closely related to the 40,000-year-old Tianyuan man fossil, DNA analysis revealed. And both the Amur female and Tianyuan man share about 75% of their DNA with the female from Mongolia’s Salkhit Valley, suggesting all three belonged to interrelated groups of modern humans who moved across East Asia for at least 7000 years, Fu says.
But by the end of the LGM, about 19,000 years ago, there were no genetic or fossil traces of this earlier population. DNA from a 19,000-year-old male in the study suggests a new group had appeared in the Amur region; he was more closely related to today’s East Asian people than to the earlier modern human fossils. His genome and those of two other males in the study who lived about 14,000 years ago also are closely related to genomes from Siberian males who may be members of the population that gave rise to early Native Americans. So, the early Amur people were likely among the ancestors of ancient and living Siberians—and distant relatives of some Native Americans—Fu says.
The three males were likely part of a group that was ancestral to today’s northern East Asians, but not southern East Asians, DNA analysis reveals. That suggests those two populations split at least 19,000 years ago, 9000 years earlier than previously thought.
The DNA evidence paints a complex picture of the ebb and flow of human populations in northeast Asia, says archaeologist Nicolas Zwyns of the University of California (UC), Davis. “There were multiple population replacements, as well as long periods of continuity.” The LGM may have triggered one of those replacements, but it’s not clear what led to other population turnovers, Fu says.
“With the ancient DNA evidence over such a long time span, these authors were actually able to test hypotheses rather than just describe patterns,” says Leslea Hlusko, a biological anthropologist at UC Berkeley and the Spanish National Research Centre for Human Evolution. “It’s a great sign for the science of ancient DNA.”
Source: Science Mag