In an announcement sure to spark a firestorm of controversy, researchers say they’ve found signs of ancient humans in California between 120,000 and 140,000 years ago—more than a hundred thousand years before humans were thought to exist anywhere in the Americas.

If the researchers are right, the so-called Cerutti mastodon site could force a rewrite of the story of humankind.

“I realize that 130,000 years is a really old date and makes our site the oldest archaeological site in the Americas,” says study leader Tom Deméré, the paleontologist at the San Diego Natural History Museum, whose team describes their analysis today in Nature. “Of course, extraordinary claims like this require extraordinary evidence, and we feel like the Cerutti mastodon site