Each of these claims was a bold one. “We archaeologists had a tough-enough time accepting that there are sites in the Americas greater than 13,000 years old—and a few of us still haven’t accepted that,” says Bonnie Pitblado from the University of Oklahoma. “But 130,000 years—ten times that far back in prehistory? That’s an enormous leap for a profession that, for all its focus on changes in human culture through time, really does not like to change its views.”

“If the authors are correct, it would completely rewrite our best understanding of the peopling of the Americas,” says Jon Erlandson from the University of Oregon. “As scientists we're supposed to keep an open mind, but I doubt that many archaeologists will be convinced by this case. Extraordinary claims require extraordinary evidence, and I didn't find it here.” David Meltzer from Southern Methodist University concurs. “If you are going to push human antiquity in the New World back more than 100,000 years in one fell swoop, you’ll have to do so with a far better archaeological case than this one,” he says.

Most of the experts I spoke to weren’t convinced by the presented evidence, and some were downright disdainful. “I was astonished, not because it is so good but because it is so bad,” says Donald Grayson from the University of Washington.

But not everyone is ready to dismiss the study yet. “This paper is a fantastic hypothesis,” says Zeray Alemseged from the University of Chicago. If the team is right, the perpetrators who broke the mastodon couldn’t possibly have been Homo sapiens, since our species hadn’t left Africa 130,000 years ago. But at the time, the planet was full of other hominids, including Homo Erectus, Neanderthals, Denisovans, and the “hobbits” of Flores. “Could it be that some of them ventured into North America, back then? Why not? Could there have been another species of Homo hanging out in California? Knowing how migratory our genus is I wouldn’t be surprised.”

“I think they’ve have made a very strong case,” says Pitblado. “They presented compelling evidence that doesn’t make this site a slam dunk, but must be taken seriously. I predict that most archaeologists will roll their eyes. What they’re unlikely to do is give the site a chance.”



A schematic of the Cerruit mastodon, showing recovered bones and teeth. Dan Fisher & Adam Rountrey, University of Michigan.

Since 1993, the team, including lead author Steven Holen, have repeatedly tried to date the mastodon fragments, using techniques like carbon-dating. They repeatedly failed. They only succeeded when they turned to uranium-thorium dating, which looks at the decay of two radioactive elements. That gave an age of 130,700 years, give or take 9,400 in either direction.

“There are a small number of uranium-thorium dating specialists who think bone can be dated,” says John Hellstrom from the University of Melbourne—who isn’t one of them. “The problem is that uranium moves around in bone, which invalidates the dating unless you can use a mathematical model of that movement to compensate. That is exactly what the authors of this study have tried to do.” Coupled with other evidence about the surrounding rock layers, the bones are “likely to be something around the age the authors claim,” he says, “but I would not give these dates hard-evidence status. More correctly, they indicate the bones are most likely at least tens of thousands of years in age.”