The New York Times reports:

Of all the long-running disputes in archaeology, few roil scholars more than the question of when humans arrived in the Americas. For much of the past century, the reigning theory was that in or around 11,500 years ago big-game hunters from Asia trudged to North America across a land bridge spanning the Bering Strait, hung a right through a corridor between glaciers and, in less than a millennium, reached the tip of South America.

Over the past three decades, however, archaeological research has made it increasingly clear that the hunters were preceded by much earlier cultures that colonized the Americas between 24,500 and 16,000 years ago.

This week a new academic study upended even those migration timelines by proposing that what is now central-west Brazil was settled as early as 27,000 years ago, a finding that bolsters the theory that our ancestors inhabited the continent during the Pleistocene Epoch, which ended around 11,700 years ago. The period is also called the Ice Age because of its numerous cycles of glacial formation and melting.

The conclusions of the paper, published in the journal Proceedings of the Royal Society B, are based on an analysis of an improbable source: three bones from an extinct giant ground sloth. Excavated 28 years ago in the Santa Elina rock shelter, the fossils — similar to the hard, scaly plates, called osteoderms, that armor the skin of present-day armadillos — showed signs of having been modified into primordial pendants, with notches and holes that researchers said could only have been created by people.

“This is a really significant study because it adds to a growing body of data on the antiquity of human occupation in the Americas,” said April Nowell, a Paleolithic archaeologist at the University of Victoria who was not involved in the project. “It also shows the importance of personal ornaments.”

The giant ground sloth first appeared in South America 35 million years ago. Some species were as hefty as modern elephants and, rearing up on their hind legs, stood more than 10 feet tall. The hulking herbivore, a distant relative of today’s much smaller tree sloth, had massive jaws and powerful clawed limbs, and it may have served as inspiration for the mapinguari, a mythical beast that, in Amazonian legend, had the nasty habit of twisting off the heads of humans and devouring them. The giant sloth disappeared from the continent some 11,000 years ago, but fossil remains abound. [Continue reading…]