The answer to when humans first arrived on the American continents is a divisive issue that raises a lot of eyebrows. And a new paper based on work done at the San Diego Natural History Museum suggests a whole new set of ideas about when people might have been in the Americas. The research concerns the findings circulating around a mastodon found in southern California next to a freeway about 20 years ago.

Nature published a paper that examines mastodon bones that appear to have been butchered with primitive stone tools for their marrow. This is not that uncommon a find per se — we know early humans ate mastodons all the time. What is shocking for the scientific community is that these bones date from 130,000 years ago. There’s seemingly no question from the scientific community to the veracity of the radiocarbon dating of the mastodon. But whether it’s a site with human interaction, that’s where the question marks start coming up.

The researchers concluded after 20 years of study that scratches on bone fragments from the mastodon match rounded rocks found nearby and were therefore probably made by our ancestors. The findings have already come under fire for jumping to conclusions. Donald K. Grayson, an archaeologist at the University of Washington, said that the study failed “to rule out more mundane explanations for markings on the bones.” Which, sure, anything is possible when something’s been buried for over 100,000 years.

However, according to the paper, the conclusion wasn’t easily arrived at. The researchers partnered with outside experts to examine the methods of the bones and the stones. Basically, they used similar sized fresh elephant bones and similar rounded rocks to imitate what they found in the ground. The researchers observed that their test bones broke at the same angles and scattered onto the ground in the same patterns as what they dug up. While that’s not conclusive, it is compelling. Moreover, another team of independent researchers examined the rocks and found that scratches on the rocks matched those on the bones. Understandably, it’s hard to fathom how that could happen without a humans using a rock as a tool to rustle up some supper.

The head of the study, Dr. Thomas A. Deméré, puts it this way, “some people are just going to say it’s impossible and turn away.” He continues, “we could be wrong. But people have to be open to the possibility that humans were here this long ago.” Dr.Deméré goes on to say that the findings only lead to more questions — like were their Neanderthals in North America? Or maybe Denisovans? Or maybe some form of the homo species that is currently unknown to science? And if it was Homo Sapiens, then, wow, does that change a few ideas about human migrations?

So many new questions! Now let’s do some more digging and science-ing and find out some of these answers.

There’s strong evidence now that animals and humans have been crossing land bridges and sailing to and from the Americas for far longer than ever originally thought. National Geographic recently pointed out that at best the whole idea of when or how the indigenous peoples came to the Americas is full of “some long-standing puzzles … which include genetic oddities and archaeological inconsistencies.” And this only seems to add to the oddities and inconsistencies.

(Via Nature)