An Ice Age site in San Diego, Calif., preserves 130,000-year-old bones and teeth of a mastodon that show evidence of modification by early humans. Analysis of these finds dramatically revises the timeline for when humans first reached North America, according to new research. The fossil remains were discovered by Museum paleontologists during routine paleontological mitigation work at a freeway expansion project site managed by the California Department of Transportation (Caltrans). The bones, tusks, and molars, many of which are sharply broken, were found deeply buried alongside large stones that appeared to have been used as hammers and anvils, making this...