Chinese Roots Lie in Africa, Research Says
Most of the population of modern China--one-fifth of all the people living today--owes its genetic origins to Africa, an international scientific team said today in research that undercuts any claim that modern humans may have originated independently in China.
In the search for human origins, in which political beliefs and pride of place can figure as prominently as fossil evidence, the genetic findings dramatically illustrate the intricate weave of prehistoric migrations and human evolution, the scientists said.
Published today in the Proceedings of the National Academy of Sciences, the study is the product of the Chinese Human Genome Diversity Project, a consortium of seven major research groups in the People’s Republic of China, and the Human Genetics Center at the University of Texas Health Science Center at Houston. It was funded by the National Natural Science Foundation of China.
Detailed Genetic Profiles Created
The group used the advanced tools of DNA analysis to create detailed genetic profiles of 28 of China’s official population groups, which comprise more than 90% of the country’s population, to better understand the roots of complex chronic diseases like diabetes and hypertension. By exploring the genetic relationships that exist today among so many of China’s ethnic groups, the team also shed light on the ancestry of people in East Asia, who, like everyone, carry in every cell of their bodies genetic hints about their evolutionary history and the journeys of their forebears.
“The contribution [of this study] is very significant to the literature of human evolution,” said Ranjan Deka at the University of Cincinnati, who studies human genetic variation. “The findings also will have a lot of bearing in the study of genetic diseases.”
Until now, other researchers said, few studies of human population genetics have taken such a comprehensive look at China. Stanford University geneticist Luca Cavalli-Sforza, an authority on human genetic variation, said, “It is very encouraging to see a cooperative effort of this magnitude beginning to take place in this most important part of the world, and [they] are to be warmly congratulated for it.”
In all, the Chinese government today recognizes 56 ethnic groups. Just one of them, the Han, makes up the bulk of the population, comprising about 1.1 billion people. The other 55 ethnic minority groups encompass about 100 million people spread throughout China.
To study the diverse genetic inheritance of such an enormous population, the researchers used a special set of genetic markers called microsatellites. These extremely short chemical segments of DNA mutate very rapidly. That allows scientists to use them as signposts to mark how populations diverged or merged over time, reconstructing their evolutionary journey through time and across the continents to their contemporary abodes.
The scientists looked at 30 such microsatellite markers across 28 of the population groups in China and then compared the pattern to 11 other population groups around the world.
The researchers demonstrated that the peoples of northern and southern China cluster into distinct regional genetic populations that share inherited characteristics. Those groups, in turn, can be divided into even smaller, separate genetic groups.
Yet, overall they all are descendants of a single population group that may have migrated into China from the south eons before humans learned to forge metal tools or use a written alphabet, the new research suggests.
“Populations from East Asia always derived from a single lineage, indicating the single origins of those populations,” the researchers said. “It is now probably safe to conclude that modern humans originating in Africa constitute the majority of the current gene pool in East Asia,” they said.
Although few scholars today dispute the idea that the earliest ancestors of the human species evolved in Africa, there still is considerable debate over how modern humanity evolved from its more primitive ancestors.
Many anthropologists believe that humans may have migrated out of Africa in waves. More than a million years ago, humanity’s primitive ancestors, known as homo erectus, walked out of Africa to colonize Europe, the Middle East and Asia. On that everyone agrees.
Then several hundred thousand years later, some theorize, a second wave of more sophisticated tool-using humans migrated out of Africa and overwhelmed those earlier ancestors. According to that theory, modern humans are descended solely from those especially sophisticated tool-users.
Other researchers dispute that pattern. In their view, there was no second wave of migration from Africa. Instead, modern humankind evolved in China and elsewhere as colonies of more primitive homo erectus intermarried in a global network of genetic relationships.
Study Finding Not Disputed
“The issue,” said University of Michigan anthropologist Milford Wilpoff, “is about whether people have multiple ancestors from many places or one ancestor from one place.”
Wilpoff, who is a leading advocate of the multi-regional hypothesis, did not dispute the findings of the China study. In his view, it is measuring the genetic effects of population shifts during the relatively recent prehistoric past. “This [new finding] is dealing with events that are much younger than the issue of modern human origins,” he said.
Even so, the researchers said, the genetic evidence would not have pointed so clearly to a single lineage if an independent branch of the human family originating in Asia had made a major contribution to the continent’s modern population.
Li Jan, the senior scientist guiding the genetic analysis, said the findings may disappoint some of his fellow geneticists in China, where recent fossil discoveries that attest to the great antiquity of human settlement in East Asia have been a source of national pride.
“The genetics community in China is in favor of the idea of independent origin of the people of China,” said Jan at the Human Genetics Center in Houston. “But this is another confirmation of African origin.”
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Out of Africa, Into China
Most of the modern population of China has its genetic origins in Africa, according to research released today. Scientists say prehistoric humans may have migrated east across Southeast Asia and then turned north to settle China.
Source: Proceedings of the National Academy of Sciences