PHOTOGRAPH COURTESY SAN DIEGO NATURAL HISTORY MUSEUM
In 1992, Thomas Deméré, a paleontologist at the San Diego Natural History Museum, and several of his colleagues were called in to inspect an array of bones that had been unearthed by highway workers building Route 54, just south of the city. What turned up was the Pleistocene. The site was rich with fossils tens of thousands of years old, including the remains of a camel, a horse, a dire wolf, a ground sloth, and, most impressive, a mastodon. Today, the area stretches with ranch homes and water-restricted lawns; way back then, it was a broad floodplain with a single shallow ribbon of water winding through it. “It was a very nice place to live, I’d think, not far from the coastline,” Deméré said at a press conference yesterday.
For years now, Deméré and his collaborators have been studying specimens from the site with mounting astonishment. In 2014, James Paces, a research geologist with the U.S. Geological Survey, determined that the mastodon remains were a hundred and thirty thousand years old. On its own, this fact would not be so surprising, but a recent examination of the animal’s bones suggests that they were smashed open with large cobbles, most likely for the marrow inside. What seemed at first to be a paleontological site, in other words, could be an archeological one. If that’s the case, then it predates some of the earliest evidence of hominins in North America by more than a hundred thousand years. Eleven scientists, including Deméré and Paces, joined to publish their results today in the journal Nature.
“The scholarship over the earliest occupation of America is a battlefield,” John McNabb, an archeologist at the University of Southampton, said by phone. (Nature asked McNabb to independently comment on the paper and the team’s results.) “But those folks are arguing about differences of two hundred years here and there. This is an order of magnitude beyond anything that’s been talked about before.” McNabb, who characterized himself as “skeptical,” predicted that the announcement would be met by “an uproar—outrage, anger, utter dismissal.” Still, he said, “If it is true, it changes everything about the occupation of the Americas and the story of the movement of people out of Africa.”