DNA Study Traces European Ancestors to 10 Men

November 10, 2000 - AP

About 80 percent of Europeans arose from primitive hunters who arrived about 40,000 years ago, endured the long ice age and then expanded rapidly to dominate the continent, a new study shows.

Researchers analyzing the Y chromosome taken from 1,007 men from 25 different locations in Europe found a pattern that suggests four out of five of the men shared a common male ancestor about 40,000 years ago.

Peter A. Underhill, a senior researcher at the Stanford Genome Technology Center in Palo Alto, Calif., and co-author of the study, said the research supports conclusions from archaeological, linguistic and other DNA evidence about the settlement of Europe by ancient peoples.

``When we can get different lines of evidence that tell the same story, then we feel we are telling the true history of the species,'' said Underhill.

The study, which involved more than a dozen researchers from Stanford and Europe, appears Friday in the journal Science.

Underhill said the researchers used the Y chromosome in the study because its rare changes establish a pattern that can be traced back hundreds of generations, thus helping to plot the movement of ancient humans.

The Y chromosome is inherited only by sons from their fathers. When sperm carrying the Y chromosome fertilizes an egg it directs the resulting baby to be a male. An X chromosome from the father allows a fertilized egg to be female.

The Y chromosome has about 60 million DNA base pairs. Changes in those base pairs happen infrequently, said Underhill, but they occur often enough to establish patterns that can be used to trace the ancestry of people.

He said researchers looking at the 1,007 chromosome samples from Europe identified 22 specific markers that formed a specific pattern of change. Underhill said the researchers found that about 80 percent of all European males shared a single pattern, suggesting they had a common ancestor thousands of generations ago.

The basic pattern had some changes that apparently developed among people who once shared a common ancestor and then were isolated for many generations, Underhill said.

This scenario, he said, supports other studies about the Paleolithic European groups. Those studies suggest that a primitive, stone-age human came to Europe, probably from Central Asia and the Middle East, in two waves of migration beginning about 40,000 years ago. Their numbers were small and they lived by hunting animals and gathering plant food. They used crudely sharpened stones and fire.

About 24,000 years ago, the last ice age began, with mountain-sized glaciers moving across most of Europe. Underhill said the Paleolithic Europeans retreated before the ice, finding refuge for hundreds of generations in three areas: what is now Spain, the Balkans and the Ukraine.

When the glaciers melted, about 16,000 years ago, the Paleolithic tribes resettled the rest of Europe. Y chromosome mutations occurred among people in each of the ice age refuges, said Underhill. He said the research shows a pattern that developed in Spain is now most common in northwest Europe, while the Ukraine pattern is mostly in Eastern Europe and the Balkan pattern is most common in Central Europe.

About 8,000 years ago, said Underhill, a more advanced people, the Neolithic, migrated to Europe from the Middle East, bringing with them a new Y chromosome pattern and a new way of life: agriculture. About 20 percent of Europeans now have the Y chromosome pattern from this migration, he said.

Archaeological digs in European caves clearly show that before 8,000 years ago, most humans lived by gathering and hunting, he noted. After that, there are traces of grains and other agricultural products.

Earlier studies had traced European migration patterns using the DNA contained in the mitochondria, a key part of each cell. This type is DNA is passed down from mother to daughter.

Antonio Torroni, a researcher at the University of Urbino, Italy, who first proposed that early humans retreated to Spain during the ice age, said in a separate Science report that the Y chromosome study ``fits completely'' with the mitochondria studies.

Underhill said the Y chromosome studies are also consistent with genetic studies showing a broader picture of human migration.

In general, studies show that modern humans first arose in Africa about 100,000 years ago and thousands of years later began a long series of migrations, he said. Some groups migrated eastward and humans are known to have existed in Australia about 60,000 years ago. Other groups crossed the land bridge into the Middle East. Humans appeared in Central Asia about 50,000 years ago.

From there, the theory goes, some migrated west, arriving in Europe about 40,000 years ago. Later, some migrated east, across the Bering Straits, to the Americas.