Support WBURNew Evidence Suggests Humans Arrived In The Americas Far Earlier Than ThoughtPlay03:32Download AudioChristopher JoyceApril 26, 2017 Share(Left) A close-up view of a spirally fractured mastodon femur. (Right) A boulder discovered at the Cerutti Mastodon site in San Diego County thought to have been used by early humans as a hammerstone. (Tom Démeré/San Diego Natural History Museum)
