Descent of Man
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Study traces genetic origin of Chinese to Africa
Posted: Thursday, January 10, 2002
by Robert Lee Hotz, Los Angeles Times, Sept 29, 1998

Most of the population of modern China owes its genetic origins to Africa, an international scientific team reports 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 much as fossil evidence, the new genetic findings dramatically illustrate the intricate weave of prehistoric migrations and human evolution, the scientists said.

The researchers also 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 eons before humans learned to write or forge metal tools, the new research suggests.

Published in today's edition of 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 at Houston. It was funded by the National Natural Science Foundation of China.

The group used the advanced tools of DNA analysis to create detailed genetic profiles of 28 of China's official population groups, which make up more than 90 percent of the country's population, to try to understand the roots of complex chronic diseases such as diabetes and hypertension.

By exploring the genetic relationships among 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 to their evolutionary history and the journeys of their forebears.
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 55 other ethnic minority groups encompass about 100 million people.

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 lets scientists use them as signposts to mark how populations diverged or merged over time, reconstructing their evolutionary journey across time and the continents to their present homes.

The scientists looked at 30 such microsatellite markers across 28 of the population groups in China and compared the pattern to 11 other population groups around the world.

"Populations from East Asia always derived from a single lineage, indicating the single origins of those populations," they 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.

While 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 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. By that theory, modern humans are descended only from those sophisticated tool-users.

Other researchers dispute that pattern. In their view, there was no second wave of migration from Africa. Instead, they believe, humankind evolved in China and elsewhere as colonies of more primitive Homo erectus intermarried in a global network of genetic relationships.

"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."

Copyright 2002 The Seattle Times Company

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