The Cerutti Mastodon site in San Diego County, California, preserves a juvenile male American mastodon and other animal remains buried in Pleistocene stream deposits about nine feet below the surface. Discovered during State Route 54 expansion work, it was excavated in 1992 and 1993 by a San Diego Natural History Museum team. Its significance centers on five worn cobbles found with the bones and on fractures that some researchers interpret as evidence that fresh mastodon bones were deliberately broken with hammerstones and anvils about 130,700 years ago. If correct, that would suggest a very early Homo presence in the Americas, but the claim remains heavily disputed.