Humans May Have Come To America 100,000 Years Earlier Than We Thought

The broken bones of an extinct animal could upend the accepted history of humans in the Americas, raising new questions about when the land was settled and by who. Researchers contend the evidence indicates that humans arrived more than 100,000 years earlier than thought.

In a new paper published in the journal Nature, Steven Holen and a team of other paleontologists at San Diego Natural History Museum argue that bones discovered in the 1990s in California are around 130,000 years old and indicate the humans were present at the time.

Scientists have generally agreed that humans arrived in North America around 20,000 years ago by crossing a land bridge from Asia in the area now known as the Bering Strait. The new evidence may rewrite our species' history.

“It’s such an amazing find and — if it’s genuine — it’s a game-changer. It really does shift the ground completely,” John McNabb, a palaeolithic archaeologist at the University of Southampton, told Nature. “I suspect there will be a lot of reaction to the paper, and most of it is not going to be acceptance.”

The potential rewrite of history is not based on human bones but those of a mastodon, an extinct relative of elephants. After the bones were found during road work in suburban San Diego, Tom Deméré of the San Diego Natural History Museum led a five-month excavation of the site, and his crew uncovered teeth, tusks and bones of the mastodon.

The mastodon bone in question shows signs of being broken on a surface with a rock, in a process akin to using an anvil, the researchers argue. The finding was interesting enough on its own, but when the researchers used radioactive uranium and thorium deposits in the bone to determine its age, they found that it was 130,000 years old.

Pontus Skoglund, a population geneticist at Harvard Medical School in Boston, said that if the discovery holds up, “it would be one of the most Earth-shattering revisions of our view of the peopling of the world”.

Some researchers, though, are skeptical. Dating methods can be faulty, and there may be alternate explanations to human activity. There are no cut marks on the bones, which would be expected if humans carved up the animal for meat. No other tools or evidence of technology were found at the discover site.

"The evidence from the Cerutti Mastodon site has been rigorously researched and presented, and might be more difficult to refute, even though the proposed hominin narrative derived from these data has some gaping holes that need filling," Erella Hovers, an archaeologist at the Hebrew University of Jerusalem, writes in a commentary on the study. "Time will tell whether this evidence will bring a paradigm change in our understanding of processes of hominin dispersal and colonization throughout the world, including in what now seems to be a not-so-new New World."

Photo credit: Nature Video screenshot via YouTube