A study of skulls excavated from the tip of Baja California in Mexico suggests that the first Americans may not have been the ancestors of today's Amerindians, but another people who came from Southeast Asia and the southern Pacific area.
The question of who colonized the Americas, and when, has long been hotly debated. Traditionally, Native Americans are believed to have descended from northeast Asia, arriving over a land bridge between Siberia and Alaska some 12,000 years ago and then migrating across North and South America.
But recent research, including the Baja California study, indicates that the initial settlement of the continent was instead driven by Southeast Asians who occupied Australia 60,000 years ago and then expanded into the Americas about 13,500 years ago, prior to Mongoloid people arriving from northeast Asia.
The skulls from Baja California, which may date back only a few hundred years, have slender-looking faces that are different from the broad-cheeked craniums of modern Amerindians, the descendants of the Mongoloid people.
"Our results change the traditional idea that all modern Amerindians present morphological affinities with East Asians as a result of a single migration," said Rolando González-José of the University of Barcelona, Spain, who led the study. "The settlement of the New World is better explained by considering a continuous influx of people from Asia."
The new study is reported in this week's issue of the science journal Nature, and could further fuel the controversy surrounding the origins of the first Americans, which is a controversial issue for American Indians in particular.
Conventional wisdom says that Native Americans descended from prehistoric hunters who walked from northeast Asia across a land bridge, formed at the end of the Ice Age, to Alaska some 12,000 years ago. American Indians resemble the people of Mongolia, China and Siberia.
In the 1930s, archeologists found stone spear points among the bones of mammoths near Clovis, New Mexico. Radio carbon dating in the 1950s showed that the oldest site was 11,400 years old. The sites were assumed, for years, to be the first evidence of human occupation in the Americas.
But more recent discoveries challenge the Clovis story. In 1996, archeologists in southern Chile found weapons and tools dating back 12,500 years. In Brazil, they found some of the oldest human remains in the Americas, among them a skeleton—named Luzia—that is more than 11,000 years old.
Luzia did not look like American Indians. Instead, her facial features matched most closely with the native Aborigines in Australia. These people date back to about 60,000 years and were themselves descended from the first humans who probably originated in Africa.
The researchers believe Luzia was part of a people, referred to as "Paleoamericans," who migrated into the Americas—possibly even by boat—long before the Mongoloid people. These Paleoamericans may later have been wiped out by or interbred with Mongoloids invading from the north.
Evolving in Isolation
The late skulls found in Baja California are similar to Luzia and the Paleoamerican skulls found in South America. Their craniums are characterized by long and narrow vaults, with faces short and low in relation to the neurocranium.
"Skeletal studies demonstrate that skeletal remains do not fit the Mongoloid set of traits that is determinant of the modern Amerindian morphology," said González-José. "Our results demonstrate that not only are some early remains not Mongoloid, but also some modern groups, like those of Baja California."
The study suggests that Baja California was one of many isolated pockets throughout the Americas were Paleoamerican traits survived. The Paleoamericans might have split at one point, with one group going down to Baja California. This group may not have come in contact with Paleoindians for millennia.
Some experts, however, find it difficult to believe that such a population could have evolved in isolation.
"I don't doubt there's skeletal diversity and that it's probably coming out of old world Asia," said Tom Dillehay, an archeologist at the University of Kentucky in Lexington, who commented on the study in a separate article for Nature. "But I am very skeptical of a population, particularly close to a coastline, that could have been isolated for more than 10,000 years."
The identity of the first Americans is an emotive issue for American Indians, who believe their ancestors were the first to inhabit the Americas.
Controversy erupted after skeletal remains were found in Kennewick, Washington, in 1996. This skeleton, estimated to be 9,000 years old, had a long cranium and narrow face—features typical of people from Europe, the Near East or India—rather than the wide cheekbones and rounder skull of an American Indian.
A coalition of Indian tribes, however, said that if Kennewick Man was 9,000 years old, he must be their ancestor, no matter what he looked like. Invoking a U.S. federal law that provides for the return of Native American remains to their living descendants, the tribes demanded a halt to all scientific study and the immediate return of the skeleton for burial in a secret location.
The matter is still stuck in the courts.