In this April 28, 1993 photo provided by the San Diego Natural History Museum, a bulldozer refills the Cerutti Mastodon site in San Diego, Calif., after the excavation and salvage of fossils. In a report released on Wednesday, April 26, 2017, researchers say the southern California site shows evidence of human-like behavior from about 130,000 years ago, when bones and teeth of an elephant-like mastodon were evidently smashed with rocks. (San Diego Natural History Museum via AP)