An archaeological dig in San Diego in 1992 may have uncovered evidence that humans arrived in North America 130,000 years ago, reports NPR. This is very significant, as it predates the (former) earliest evidence of humans in North America by 115,000 years. That's a pretty big gap, to say the least. The San Diego Natural History Museum announced the findings to the public on Wednesday.

As noted at NBC, it all started in November of 1992, when prehistoric bones were discovered at the construction site of State Route 54. Researchers dug up what would later be identified as bones belonging to a mastodon.

But that wasn't all that they found. Alongside the bones, researchers also uncovered rocks that (they say) bear signs of being used as tools. As reported at the San Diego Union Tribune, the rocks appeared to be used as hammers and anvils. Tom Deméré, a paleontologist at the San Diego Natural History Museum, told NPR that it seems that these tools were used to break mastodon bones. "The suggestion is that this site is strictly for breaking bone," said Deméré, "to produce blank material, raw material to make bone tools or to extract marrow."

It wasn't until years after the dig that scientists were able to stamp a date on the bones. Using uranium-thorium dating technology (which didn't exist in the '90s) researchers determined that the bones were 130,000 years old, which suggests that humans, too, had existed there 130,000 years ago.

“This discovery is rewriting our understanding of when humans reached the New World. The evidence we found at this site indicates that some hominin species was living in North America 115,000 years earlier than previously thought,” Judy Gradwohl, president and CEO of the San Diego Natural History Museum, said in a statement.

There are skeptics, however. Experts point to several curiosities about the dig site. For one thing, evidence suggests that the tools were only used for breaking bones, and not for extracting meat. "This is weird," John Shea, an archaeologist at New York's Stony Brook University, told NPR. "It's an outlier in terms of what archaeological sites from that time range look like everywhere else on the planet."

Donald Grayson, an archaeologist at the University of Washington, said that the conclusion was faulty, saying that it may be a mistake to draw a connection between the bones and the rocks. "It is one thing to show that broken bones and modified rocks could have been produced by people," Grayson wrote to NBC. "It is quite another to show that people, and people alone, could have produced those modifications."

So, ¯\_(ツ)_/¯.

Speaking of fossil finds at construction sites; here in L.A., Metro workers have recently come across some cool bones while digging for the Purple Line extension.