Study claims humans were in North America 130,000 years ago

Humans may have arrived in North America 130,000 years ago, a new study suggests today in Nature.

Why it matters: This means humans may have arrived in North America much earlier than previously thought, surpassing previous evidence of human activity in North America — showing activity 15,000 to maybe 30,000 years ago — by 100,000 years.

The remains: Bones of a mastodon (a relative of elephants) had spiral fractures, indicating they were broken by the hammerstones and anvils surrounding the remains, indicating humans killed the mastodon.

The skeptics: John Hellstrom of the University of Melbourne told The Atlantic the technology used to date the remains makes it so you can't pin down the age of 130,000 years. Archaeologist Donald Grayson cautioned there could be other explanations for the marking on the bones.