Gene Studies Trace Most Indians to One Migration

More than 95% of all North and South American Indians are descended from a small band of hardy pioneers that included perhaps as few as four women, who crossed the Bering Strait from Asia between 15,000 and 30,000 years ago, according to new studies of the American Indians’ genetic inheritance.

Their descendants spread out to become tribes as disparate as the Algonquins of the U.S. Northeast, the Maya of Central America and the Ticuna of South America, geneticist Douglas Wallace of Emory University said in an interview Friday.

The new evidence provides very strong support for a minority of embattled linguists who have been arguing that as many as 600 extant Indian languages may have derived primarily from one common precursor. The new results suggest that the ancient language was spoken by a single, small band of immigrants and refute the idea that the 600 tongues evolved from hundreds of languages brought by multiple waves of immigrants.

Wallace reached his conclusion by studying the genetics of mitochondria, small, energy-producing bodies found in each cell of humans. Mitochondria contain unique genetic information separate from that contained in the nucleus of cells.

By charting similarities and differences among mitochondria genes in cells from widely separated groups of Indians, Wallace was able to show that the groups had common ancestors that must have migrated to the Americas together.

“The question we were addressing was, ‘Are (the linguists who favor one predecessor language) correct? Was there a single migration that accounts for the majority of Amerindians?’ ” Wallace said. “And the answer is clearly yes.”

“I’m very pleased . . . after the drubbing we’ve been taking” from colleagues, said anthropological geneticist Steven Zegura of the University of Arizona, one of the originators of the concept of a small number of core languages. “This makes me very happy.”

The language dispute has been festering through much of the 1980s, while the time of the first migrations to the Americas has been a subject of debate for decades.

Virtually all researchers agree that American Indians are descendants of Asians who migrated across the narrow Bering land bridge from what is now the Soviet Union to Alaska. The land bridge is exposed when the level of the oceans drops as large volumes of water are trapped in polar ice during a period of global cooling.

There is general agreement that two other waves of migration occurred relatively recently--6,000 and 4,000 years ago. These waves brought the Indians who speak two language groups known as Na-dene, spoken mainly by natives of northwestern Canada, but also by the Apache and Navajo nations, and Eskimo-Aleut, spoken mainly by residents of Alaska and the northern rim of Canada.

But there has been great dispute about the origin of the 600 languages, known collectively as Amerind, that originated much earlier, between 15,000 and 30,000 years ago. The crux of the dispute is whether there was one brief period of migration across the Bering Strait or whether there were successive waves of immigration by different ethnic groups. Linguists have attempted to answer that question by comparative studies of the more than 1,000 languages that have been spoken at one time or another by American Indians.

But the linguists have broken into two fractious camps. One small group, headed by Zegura, linguist Joseph H. Greenberg of Stanford University and anthropologist Christy G. Turner II of Arizona State University, argues that all the Amerind tongues derived from one predecessor.

The bulk of linguists, in contrast, argue that Amerind represents as many as 200 different core languages, suggesting wave after wave of migrations across the Bering Strait.

The debate at times has been vitriolic. Most linguists consider the research of Greenberg and his colleagues shoddy and unscientific. Their theories “should be shouted down,” in the words of linguist Lyle Campbell of Louisiana State University.

Greenberg, in turn, scoffs at the idea of so many waves of migration. That would have required a “traffic controller at the Bering Strait,” he quipped.

Wallace’s results with mitochondria tend to support Greenberg and his colleagues. His research is based on the fact that mitochondrial genes are passed directly from mothers to children with no input from the fathers, so they are changed over long periods only by random mutations.

Studies of the difference in genetic content of mitochondria can be used to determine how closely related two individuals are and how long ago they shared a common ancestor. Such studies have been used to reveal the existence of “the mother of us all,” an African woman living 100,000 to 200,000 years ago from whom all modern humans are descended.

Wallace studied blood samples from three widely disparate Amerind groups: Pima-Papago Indians in Arizona, Maya from the Yucatan peninsula and Ticuna from the upper reaches of the Amazon in Brazil. He concluded that all were descended from a small group of women, perhaps as few as four, that immigrated to the Americas at one time.

Because those four contemporaries were from one tribe and presumably shared one language, that language must have been the prototype for all the languages now spoken by Amerinds. The predecessors of the Na-denes and the Eskimo-Aleuts presumably then migrated into the Americas at a later date. They were not able to migrate as far southward because those lands were already occupied.