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It is pretty well agreed that Homo sapiens spread out of Africa about 100,000 years ago and traveled across Asia about 60,000 years ago. 10,000 years later, they made it into Europe and Australia. They ultimately migrated down finally Pacific coast of both North and South America, and probably interior continental locations by 13,500 to 15,000 years ago.

Rock fragments found near part of a mastodon tusk in San Diego, California, suggest that a hominin species lived there about 130,000 years ago. The finding could dramatically alter the narrative of when humans arrived in North America. San Diego Natural History Museum

Rock fragments found near part of a mastodon tusk in San Diego, California, suggest that a hominin species lived there about 130,000 years ago. The finding could dramatically alter the narrative of when humans arrived in North America. San Diego Natural History Museum

A new incredible finding published today in the journal Nature, upends this current understanding of when humans arrived in North America and the peopled of the Americas. The story of this begins in fall of 1992, as a construction crew discovered a bounty of bones while creating a sound berm for a freeway expansion in a coastal area of San Diego County. The site is known as Cerutti.  Among the skeletal remains of dire wolves, camels, horses and gophers was the most intriguing remains of an adult male mastodon.

Mastodon skeleton schematic showing which bones and teeth of the animal were found at the site. (Dan Fisher and Adam Rountrey, University of Michigan)

Mastodon skeleton schematic showing which bones and teeth of the animal were found at the site. (Dan Fisher and Adam Rountrey, University of Michigan)

Center for American Paleolithic Research archaeologist Steve Holen and lead author of the current paper was part of the archaeological dig since in the ’90’s. His two decade project lead to him also finding an abandoned campsite, where humans had left stone tools and hammered mastodon bones behind. The video below from the initial discovery documents the finding along with the lithics.

The surface of mastodon bone showing half impact notch on a segment of femur. (Tom Deméré, San Diego Natural History Museum)

The surface of mastodon bone showing half impact notch on a segment of femur. (Tom Deméré, San Diego Natural History Museum)

The assorted mastodon remains, included two tusks, three molars, 16 ribs, and more than 300 bone fragments. These fragments bore impact marks suggesting that they had been smacked with a hard object. The picture to the right documents this. Some of the shattered bones contained spiral fractures, indicating that they were broken while still “fresh,” the authors write. The five hulking stones stools were hammers and anvils, and showed signs of impact suggesting that the bones had been smashed in that location. The breaks and scoring marks on the bones suggest that people were breaking them open to get at the marrow, as well as crafting them into tools.

For the last two decades, attempts at radiocarbon dating were unsuccessful because the bones did not contain a sufficient amount of carbon. So the team turned to uranium–thorium dating. This technique is used on carbonate sediments found on bones and teeth. It makes it possible to date objects far older than 50,000 years, the upper limit of radiocarbon dating. Using this method, scientists were able to assign an approximate age of 130,000 years to the Cerutti bones.

This is a huge claim. It is outrageous to some degree, because this date is 115,000 years older than most people would accept as the earliest occupation of the Americas. Most archaeologists generally agree that humans populated the Americas around 14,500 years ago. The Clovis people, once thought to be the first humans to enter the Americas, lived about 13,000 to 11,000 years ago, other studies have heated the debate, placing humans in the Calico Hills in California 50,000 to 80,000 years ago and in Brazil 20,000 to 40,000 years ago, and in Canada’s Yukon Territory as early as 24,000 years ago. But 130,000 years ago is unheard of, a magnitude of difference. This leaves me speechless.

The breaks in mastodon bones found at a research site in California matched the breakage patterns that the researchers observed when they used stones to hammer elephant and cow bones in experiments. Kate Johnson/San Diego Natural History Museum

The breaks in mastodon bones found at a research site in California matched the breakage patterns that the researchers observed when they used stones to hammer elephant and cow bones in experiments. Kate Johnson/San Diego Natural History Museum

Just to make sure these kinds of stone tools could damage mastodon bones in the way they found them at Cerutti Mastodon, Holen and his colleagues conducted several experiments. They built stone-age tools and smashed elephant bones. After several such experiments, it was clear that one of the only ways to produce the damage they saw on those 130,000-year-old mastodon limbs was to crush them with rock cobbles on rock anvils. To bolster their theory, researchers analyzed mastodon bones found in later North American sites, which date from 14,000 to 33,000 years ago. These bones displayed the same fracture patterns that were observed among the remains of the Cerutti Mastodon

Many are skeptics, using this single line of evidence, albeit a bit abstract and questionable. Who were these people? In their paper, the authors suggest that the humans whose tools they found in California might have been Neanderthals or Denisovans. Probably, they conceded, these humans were a hybrid of several early humans, and possibly even a form of early Homo sapiens who roamed Asia more than 200,000 years ago.

What do you think? Is this evidence sound? Is it enough to re-write our understandings?

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