Dig uncovers previously unknown North American culture.
The long-standing idea that the Clovis people of ancient North America were the first tool-using humans on the continent 13,200 years ago is being overturned by the discovery of human artefacts in a Texan creek bed that are even older.
Michael Waters, a geoarchaeologist at Texas A&M University in College Station, and his team unearthed more than 15,000 stone artefacts from the Debra L. Friedkin archaeological site in Texas. Using luminescence dating, which dates the last time samples were exposed to sunlight, the researchers found that the artefacts are between 13,200 and 15,500 years old. They seem to have been left undisturbed by any sort of soil movement, suggesting that the artefacts come from a time before the Clovis people came to dominate the landscape.
"With these sorts of soils it is easy for objects to move around over time, but with 15,000 artefacts in the pre-Clovis horizon that would involve a whole lot of transport," says Rolfe Mandel, a geoarchaeologist at the University of Kansas in Lawrence who was not involved in the study, which is published online today in Science. "A lot of archaeological studies like this have problems, but this one is about as perfect as they come, there is little to question here."
The finding does not, however, suggest that the Clovis people simply lived in North America earlier than previously believed. Instead, it hints that a different group of people using different tool types was present during the earlier years. This group could have been replaced by or culturally evolved into the Clovis.
Although most of the newly recovered artefacts are debris such as bits of chipped stone, Waters and his team have uncovered 56 stone tools made from chert. Twelve of these are bifaces, two-sided sharp-edged stone tools made through flaking and chipping. They seem to have been used as knives and choppers on both soft and hard materials. Crucially, a few of these tools are similar to the iconic, lance-like spear points that the Clovis people made, but they are simpler and recognizably different.
"The tools seem to be locally technologically ancestral to those used by the Clovis," says James Adovasio, an archaeologist at Mercyhurst College in Pennsylvania.
The toolkit of these pre-Clovis people is also lighter than that used by the Clovis culture. "This suggests they were mobile hunter–gatherers, readily moving across the landscape — quite different from the Clovis people who had heavier tools and were sedentary," says Waters.
Last nail in the Clovis coffin
It is not entirely surprising that the Clovis people developed their impressive spear points in southern North America from simpler tools. Genetic studies indicate that the Clovis people hailed from northeast Asia. The only plausible path for them to have made it to North America was via a gruelling journey over the Alaskan land bridge, which once connected Asia and North America and through glacial corridors in Canada. "People have assumed that they developed their spear points along the journey into North America and then quickly used them to drive many species to extinction," says Adovasio. Yet none of the iconic Clovis spear tips has ever been found in Asia, in Alaskan sediments dating to the time when they probably made their migration or in the Canadian glacial corridor.
"It never made sense to me that the spear points originated during the migration. Now that we have biface technology at pre-Clovis sites in the continental United States, it seems that this is where Clovis technology developed and spread from," says Waters.
"I think we can safely say this work puts another nail in the Clovis-first coffin," says Adovasio.
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Kaplan, M. Stone tools cut swathe through Clovis history. Nature (2011). https://doi.org/10.1038/news.2011.185