Hot on the heels of yesterday's news about the arrival of the first people in the Americas, an international team has revealed a previously-unknown culture that was flourishing just a thousand or so years later.
Archaeologists say they've found evidence in Oregon's Paisley Caves that Western Stemmed projectile points - darts or thrusting spearheads - were being used at least 13,200 years ago, during or before the well-known Clovis culture in western North America. It may well be the first direct evidence of humans on the continent.
The new conclusions are based on 190 radiocarbon dates of artifacts, coprolites - dried feces - bones and sagebrush twigs meticulously removed from well-stratified layers of silt in the ancient caves.
But what the team didn't find, says lead researcher Dennis L Jenkins of the University of Oregon, is any evidence of the Clovis culture, such as their broad, concave-based, fluted projectile points.
Radiocarbon dating of the Western Stemmed projectiles places them in potentially pre-Clovis times. This suggests that Clovis may have arisen in the Southeastern United States and moved west, while the Western Stemmed tradition began - perhaps even earlier - in the West and moved east.
"From our dating, it appears to be impossible to derive Western Stemmed points from a proto-Clovis tradition," says Jenkins. "It suggests that we may have here in the Western United States a tradition that is at least as old as Clovis, and quite possibly older. We seem to have two different traditions co-existing in the United States that did not blend for a period of hundreds of years."
The origin of humans in the Americas has long suggested early migration out of Siberia and eastern Asia, probably across a temporary land bridge between Russia and Alaska. This theory is borne out by a DNA study appearing in Nature this week suggesting that they arrived in three waves.
The new paper doesn't address the routes early migrants may have taken, but the evidence found in the DNA of the coprolites continues to point to Siberia-east Asian origins.
"The results of this study are exciting, because they show that the hypothesis that the Clovis people were the first Native Americans, which has been the prevailing idea for the last decades, is wrong," says Michael Hofreiter of the UK's University of York.
"Now researchers need to come up with a new model for the settling of the Americas."