Archaeologists have discovered stone tools that suggest that humans reached what is now northeast Brazil as early as 22,000 years ago. This finding is contrary to a belief that people first arrived in the Americas from Asia about 13,000 years ago.
"If they are right, and there is a great possibility that they are, that would change everything we know about the settlement of the Americas," Walter Neves, an evolutionary anthropologist at the University of Sao Paulo, was quoted as saying.
The new discovery challenges the prevailing belief of 20th-century archaeology in the US, known as the Clovis model, that holds that people first arrived in the Americas from Asia about 13,000 years ago.
The stone tools were found at Serra da Capivara National Park in northeast Brazil, said a New York Times report.
"The Clovis paradigm is finally buried," Eric Boeda, the French archaeologist leading the excavations, commented.
However, scholars in favour of the Clovis model have quickly rejected the findings.
According to Gary Haynes, an archaeologist at University of Nevada, Reno, the stones found were not tools made by humans but could have become chipped and broken naturally by rockfall.
Another archaeologist Stuart Fiedel said that monkeys, including large extinct forms, might have made the tools instead of humans.
Archeologist Dr Tom Dillehay immediately dismissed Fiedel's claim, stating that "to say monkeys produced the tools is stupid".
At the same time, discoveries elsewhere in Brazil are adding to the mystery of how the Americas were settled, the report said.