Researchers in Southern California say they've uncovered evidence that humans lived there 130,000 years ago.
If it's true, it would be the oldest sign of humans in the Americas ever — predating the best evidence up to now by about 115,000 years. And the claim has scientists wondering whether to believe it.
In 1992, archaeologists working a highway construction site in San Diego County found the partial skeleton of a mastodon, an elephant-like animal now extinct. Mastodon skeletons aren't so unusual, but there was other strange stuff with it.