martes, 29 de marzo de 2011

America's first settlers lived 15000 years ago: study - AFP

WASHINGTON — Scientists excavating a creek bed in Texas found tools and other artifacts dating back 15,500 years, making it the oldest settlement site ever found in North America, a study reported Thursday.

The objects unearthed at an archaeological dig in the Buttermilk Creek complex near Austin suggested that humans settled the continent some 2,000 years earlier than previously believed.

The discovery could lead to a radical revision of who the first American inhabitants were, and when they settled the continent, the researchers said.

"We found Buttermilk Creek to be about 15,500 years ago -- a few thousand years before Clovis," Steven Forman, an environmental sciences professor, referring to a site in New Mexico.

"It's the first identification of pre-Clovis lithic technology (stone tool technology) in North America," he said, referring to a prehistoric Paleo-Indian culture dating back some 13,000 years ago.

Clovis culture was originally named for a small number of artifacts found between 1936 and 1938 at an archaeological site near Clovis, New Mexico.

The article in the March 25 issue of Science said that while artifacts suggesting earlier settlement had been found at the Texas site before, they could not be reliably dated until now. Innovative dating techniques were used on the Texas artifacts.

Scientists from the University of Illinois at Chicago determined the age of the objects by using an optical dating technique that linked sediment and mineral samples to human artifacts and tools found in a single earthen layer located below younger artifacts.

Carbon-14 dating couldn't be used to date the pre-Clovis artifact layer because that layer didn't contain any organic matter.

"We dated the sediments by a variety of optical methods," Forman said.

"We also dated different mineral fractions as well, and we consistently got the same ages," he said.

"We looked at the age structure of the sediment by many different ways and got the same answers," said Forman.

Clovis culture came to be associated with distinctively shaped "fluted" spear points, known as the Clovis point.

The Clovis people came to be regarded as the first human inhabitants of the New World some 13,000 years ago and the ancestors of all the indigenous cultures of North and South America.

The latest research suggests a more complicated story, according to the scientists, who said the newest information may change the narrative about the first American inhabitants.

"There are a lot of problems with the Clovis first model," said scientist Michael Waters of Texas A&M University, the lead researcher on the project, who said evidence points to a culture earlier than Clovis.

"First off, there's no Clovis technology anywhere in Northeast Asia. Second of all, fluted points in Alaska are made differently than those of the Clovis, and these actually date at two sites now 1,000 years younger than Clovis.

"And then, thirdly, there are six sites in South America that date to the same time period of Clovis... And these sites do not have Clovis artifacts at them."

"These facts alone lead to the conclusion that Clovis couldn't be the first Americans and that people had to have been here before Clovis," he said.

"It's basically time to abandon once and for all the Clovis first model and develop a new model for the peopling of the Americas," he said.

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