History Rewritten! Early Humans were in North America 130,000 Years Ago
An amazing find at an Ice Age site in San Diego, California may dramatically alter the accepted timeline for when early humans first reached North America. 130,000-year-old bones and teeth of a mastodon show evidence of modification by early humans.
A trove of ancient bones was found in 1992 by construction workers. It included the remains of dire wolves, horses, gophers, camels, and -the most exciting - an adult male mastodon. Ars Technica reports that It took years of testing before an interdisciplinary team of researchers could ascertain that the mastodon bones date to 130,000 years ago. But with this information in hand an even more shocking claim was waiting to be made – there are marks the researchers assert were left on the bones by early humans.
Mastodon skeleton schematic showing which bones and teeth of the animal were found at the site. ( Dan Fisher and Adam Rountrey, University of Michigan )
“I realize that 130,000 years is a really old date. Of course, extraordinary claims like this require extraordinary evidence.” Thomas Deméré, principal paleontologist at the San Diego Museum of Natural History and one of the authors of the recent study, said at a press conference .
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The team waited 24 years to ascertain their facts before publishing their findings in the journal Nature – they seem positive that the dates and details add up. As they wrote in their paper:
“The earliest dispersal of humans into North America is a contentious subject, and proposed early sites are required to meet the following criteria for acceptance: (1) archaeological evidence is found in a clearly defined and undisturbed geologic context; (2) age is determined by reliable radiometric dating; (3) multiple lines of evidence from interdisciplinary studies provide consistent results; and (4) unquestionable artefacts are found in primary context. Here we describe the Cerutti Mastodon (CM) site, an archaeological site from the early late Pleistocene epoch, where in situ hammerstones and stone anvils occur in spatio-temporal association with fragmentary remains of a single mastodon (Mammut americanum).”
They go on to describe the Cerutti Mastodon site, writing that it had spiral-fractured mastodon bone and molar fragments, many of which preserve evidence of percussion. The site also had flat rocks that could have been anvils and a collection of small stones that may have been used as hammers. These artifacts were found in the same layer as the mastodon bones and show evidence of use wear and impact marks. As Ars Technica says, the site apparently looked “like a perfectly preserved tableau of an ancient tool-making workshop.”
Center for American Paleolithic Research archaeologist Steve Holen explained the modification of the bones in more detail :
“People were breaking up the limb bones of a mastodon, removing some of the big, thick pieces. They were extracting marrow for food. And they were using old technology. We have evidence of people in Africa 1.5 million years ago breaking up elephant limb bones with this same [stone] technology.”
A view of two mastodon femur balls, one face-up and one face-down. Neural spine of a vertebra exposed (lower right) and a broken rib (lower left). The fact that some bones were broken and others weren't may be further evidence that early humans were picking and choosing which ones to crush with hammers. ( San Diego Natural History Museum )
Paper co-author and University of Wollongong archaeologist Richard Fullagar, an expert on the kinds of microdamage that humans leave behind on stone tools, further asserted the evidence of humans at the site:
“The evidence at this site is remarkable. I thought... they were pounding stones. All the materials indicated that they had been used for smashing up bones. You can see fragments of hammers and anvils that can be fitted back into the stones... It's rare that you get all that evidence at one site. It really does show humans have been there.”
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Smithsonian reports that the researchers decided to analyze and compare their findings with mastodon bones from North American sites dating from 14,000 to 33,000 years ago. The researchers also conducted experiments to see if these kinds of stone tools could damage mastodon bones in the same way they found them at Cerutti Mastodon. Their results “produced exactly the same kinds of fracture patterns that we see on the Cerutti mastodon limb bones,” said Holen , who added, “[W]e can eliminate all of the natural processes that break bones like this. These bones were not broken by carnivore-chewing, they were not broken by other animals trampling on the bone.”