The continuing controversy over how the Americas were populated entered a new phase when Anna Roosevelt, an archaeologist at the Field Museum, recently announced the discovery of a Paleoindian site in the Amazon jungles of Brazil that is contemporary with the Clovis people of New Mexico.

Conventional wisdom has it that the first settlers crossed a land bridge over the Bering Strait during the last ice age and swept rapidly down across North America in pursuit of big game such as bison and mammoth. The site at Clovis, dating to about 11,000 years ago and complete with skillfully fluted arrow and spear points, seemed to fully support this argument.

If this theory is correct than any sites in South America would have to date later than Clovis since migration would be from north to south. Moreover, it is thought that rain forests could not provide enough food to support people until the advent of slash and burn cultivation which did not come into practice for several thousand years. The first major challenge to the theory came from Niede Guidon, who claimed she found a site at Pedra Furada, Brazil, that had been continuously occupied since about 50,000 years ago. Her evidence for the earliest occupation was so weak, and the whole concept so controversial, that stronger evidence for a later occupation contemporary with the Clovis occupation went almost unnoticed. Roosevelt, whose research results recently appeared in the journal Science, has presented a case that is going to be much harder to refute.

Roosevelt’s group were excavating in the vicinity of the Amazon River in Brazil when a local led them to a large cave whose walls were covered with handprints and paintings of humans and animals. Careful excavation of the floor revealed a series of occupations with the first dating over a 1,200-year period from about 11,200 to 10,000 years ago. After this, the cave was abandoned for about 2,500 years and then taken over by a culture who had, by that time, developed shell ornaments and pottery.

No one argues about these, and later occupants, but Roosevelt has yet to win over some critics of her earliest inhabitants for the cave. It is not the evidence but its age that is being called into question. Whereas the stone artifacts Guidon claims at Pedra Furada are widely dismissed as fragments of weathering, Roosevelt can point to well-shaped points and blades at her site. These were found along with the remains of seeds, plants, fish, and small animals.

Many of the wall paintings, made with iron oxide pigment, dated from the same period. The people of the Amazon survived by gathering, fishing and hunting small animals, being denied the large game of their contemporaries to the north. Critics of Roosevelt center their arguments about the dates for the cave which were done in two labs, by two different methods, and range from 11,200 to 10,500 years ago.

This may seem like nitpicking since the difference is only 700 years, however it would be long enough for Clovis descendents to get from New Mexico to Brazil thereby keeping the accepted theory intact. Supporters say that this cannot be the case because the technology of the two cultures is completely different and could not change in that length of time even if the migration times are feasible. “This is not Clovis,” Roosevelt insists, “we haven’t got the whole story yet but something else was going on.”

In an aside, Sergio Pena published a report in Nature Genetics last year that demonstrated strong genetic links between tribes in Brazil, Mexico, and North America. “This could only be so,” says Pena, “if the natives of North and South America originated from one very small, uniform group.”

The question is: In what direction, from north to south or vice versa?

Finally, if Roosevelt’s work is correct, it raises a question about the rain forest itself. It has been commonly thought to be “virgin forest” only now being exploited by humans but now it appears that humans made an impact millennia ago. The clustering of plants, such as palms, cashews, and Brazil nuts may have come about from prehistoric human activity and the so-called virgin forests of the Amazon may be, in part, the product of human activity.

Clair Wood is a science instructor at Eastern Maine Technical College and the NEWS science columnist.