2017-An international team describes California's Cerutti Mastodon site, found in 1992. The researchers argue that the assemblage of broken mastodon bones and rocks comprises evidence of human activity. Based on measures of radioactive uranium and thorium in the bones, they argue that the site is 130,000 years old. Because this date is generally understood to precede modern Homo sapiens spreading beyond Africa, the paper suggests that Neanderthals, Denisovans or even late Homo erectus might have reached North America via the Bering Land Bridge and Pacific Coast. Nature , the paper's publisher, calls the study a "jaw-dropping claim." Parties to the announcement anticipate skepticism.