Cave find suggests humans lived in North America 30,000 years ago, not 15,000

A study published in the journal Nature shows evidence that humans have lived on this continent for much longer than previously thought.

Since 2012, a team led by Ciprian Ardelean at the Autonomous University of Zacatecas has been excavating the Chiquihuite Cave in Mexico’s Astillero Mountains. No human DNA was found at the cave, but the team found 1,930 stone artifacts, like knives scrapers and arrowheads, within a three-metre-deep stratified sequence of rock. Of the tools found, 239 were carbon dated to between 25,000 to 32,000 years old. Previously, human presence in the region was thought to have dated to between 15,000 to 16,000 years ago, based on discoveries at sites like Chile’s Monte Verde II.

A separate study, also newly published by two of Ardelean’s co-authors at the University of Oxford, took the cave evidence and combined it with findings from 41 other sites in North America, as well as a region of Siberia and western Alaska known as Beringia. Their conclusion, which matched Ardelean’s, was that humans were likely present before, during and after the period known as the Last Glacial Maximum — 26,500 to 19,000 years ago.

“It is likely that humans used this site on a relatively constant basis, perhaps in recurrent seasonal episodes part of larger migratory cycles,” the study concluded.

The Guardian reports that until recent times, it had been believed that humans first came to the Americas 13,500 years ago, by way of a Russia-to-Alaska land bridge, before making their way south across ice formations. The new study, though, throws up the possibility that some in fact made their way to this region much earlier via the Pacific, by boat.

While some scientists say some of these tools could have been shifted into lower layers inadvertently (thus giving the impression they were older than they actually are), Ardelean says the 239 oldest tools were found beneath an impenetrable layer of mud formed during the last ice age, meaning they have to be at least as old as the team surmised.

The topic is highly divisive, and dissenting voices on the new research are not hard to find. “There continues to be no convincing genetic evidence of a pre-15,000-years-ago human presence in the Americas,” geneticist David Reich told Nature.

“When I see a claim being made that is so dramatic, then the evidence has to be there to substantiate the claim,” Kurt Rademaker at Michigan State University told the same publication.

If — as Ardelean and his team feel — humans were traversing the continent much earlier than we thought, where did they go? His team did not find evidence of human DNA at the site, despite extensive digging in the dirt.
But Ardelean feels there may be a valid explanation.
“I definitely advocate for the idea of lost groups,” he told Nature, saying groups like the one which may have lived at his cave could have been wiped out by a cataclysmic event before they could pass on their genes.