Humans in California 130,000 years ago?

The evidence came from a collection of mastodon bones and ancient stones dating back to around 130,000 years ago, which appeared to have been hammered and scraped by early humans.

Construction workers in San Diego, California, discovered a cache of ancient bones while building up a highway in 1992. The remnants of dire wolves, camels, horses, and gophers were among them, but the remains of an adult male mastodon were the most fascinating.

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Two mastodon femur balls, one face up and one face down, are among the remains found at the Cerutti site in San Diego. © Image Credit: National Geographic

After years of testing, an interdisciplinary team of experts declared in April 2017 that these mastodon bones date back 130,000 years. The researchers then went on to make an even more incredible claim: these bones, they allege, bore the traces of human activity as well.

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The surface of mastodon bone showing half impact notch on a segment of femur. © Image Credit: Tom Deméré, San Diego Natural History Museum

The findings, which were published on April 26, 2017 in the journal Nature, upended archaeologists’ existing understanding of when people first arrived in North America. According to Jason Daley of Smithsonian, recent ideas suggest that humanity initially moved to the continent around 15,000 years ago over a coastal path.

However, in January 2017, archaeologist Jacques Cinq-Mars published a fresh study of horse bones from the Bluefish Caves that revealed people may have been on the continent as early as 24,000 years ago.

The current research, on the other hand, implies that some form of hominin species — early human ancestors from the genus Homo — were smashing up mastodon bones in North America 115,000 years before the widely accepted date.

That’s a rather early date, and it’s bound to raise some intriguing questions. There is no other archaeological evidence in North America that supports such an early human presence.

During a news briefing, Thomas Deméré, a chief paleontologist at the San Diego Museum of Natural History and one of the study’s authors, said, “I recognize that 130,000 years is a pretty long date.Exceptional statements like these, of course, need extraordinary evidence.”

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San Diego Natural History Museum Paleontologist Don Swanson pointing at rock fragment near a large horizontal mastodon tusk fragment. © Image Credit: San Diego Natural History Museum

Deméré and his co-authors feel that their findings at the Cerutti Mastodon site ― as the excavation region is known — provide just that. Paleontologists working at the site discovered two tusks, three molars, 16 ribs, and over 300 bone pieces, among other mastodon remnants.

Impact marks on these shards indicated that they had been slammed with a hard object. The authors state that spiral fractures were found in several of the fractured bones, indicating that they were broken while still “fresh.” Researchers uncovered five huge stones among the fine-grain sands at the location of the site.

The stones were utilized as improvised hammers and anvils, or “cobbles,” according to the study. They had impact signs — fragments recovered in the vicinity could be moved back into the cobbles — and two different groups of fragmented bones around the stones, indicating that the bones had been crushed in that spot.

At the news announcement, Deméré added, “These patterns taken together have led us to the conclusion that people were processing mastodon bones using hammerstones and anvils.”

Steven Holen, co-director of the Center for American Paleolithic Research; James Paces, a research geologist at the United States Geological Survey; and Richard Fullagar, an archaeologist at the University of Wollongong in Australia, were among his co-authors.

The team believes that the site’s inhabitants were breaking the bones to produce tools and harvest marrow because there is no indication of butchery. Mastodon bones unearthed in later North American sites, dating from 14,000 to 33,000 years ago, were studied to support the researchers’ conclusion. The fracture patterns on these bones matched those found among the Cerutti Mastodon’s remains.

By slapping at the bones of a recently died elephant, the mastodon’s closest living cousin, researchers attempted to reproduce the behavior that may have occurred at the site.

According to Holen, their efforts “created exactly the same sorts of fracture patterns as we find on the Cerutti mastodon leg bones. All of the normal mechanisms that shatter bones like this can be eliminated,” Holen noted. “These bones were not fractured by carnivores eating on them, or by other creatures stomping on them.”

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Mastodon skeleton schematic showing which bones and teeth of the animal were found at the site. © Image Credit: Dan Fisher and Adam Rountrey, University of Michigan

While some team members were wrecking elephant bones, others were attempting to date the Cerutti mastodon bones. Radiocarbon dating attempts were unsuccessful due to a lack of carbon-containing collagen in the bones. As a result, researchers turned to uranium-thorium dating, a technique commonly used to double-check radiocarbon dates.

Uranium–thorium dating, which can be used on carbonate sediments, bones, and teeth, allows scientists to date objects much older than the 50,000-year limit set by radiocarbon dating. Scientists were able to estimate the age of the Cerutti bones at 130,000 years using this method.

While the authors of the study believe their evidence is unmistakable, other experts have been remained skeptical. Briana Pobiner, a paleoanthropologist with the Smithsonian Institution’s Human Origins Program, says it is “nearly impossible” to rule out the possibility that the bones were broken by natural processes, like sediment impaction.

The authors of the study have anticipated that their conclusions will be met with some wariness. “I know people will be skeptical of this because it is so surprising,” Holen said during the press conference. “I was skeptical when I first looked at the material myself. But it’s definitely an archaeological site.”

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Restoration of an American mastodon. © Image Credit: Public Domain

Researchers also acknowledged that for now, the study raises more questions than it answers. For instance: Who were the early people described by the research, and how did they arrive in North America? “The short answer is that we don’t know,” Fullagar stated.

Researchers believe these folks, whatever they were, crossed the Bering land bridge or sailed up the coast to reach North America. Early people in other regions of the world may have been able to traverse water, according to research.

According to Heather Pringle of National Geographic, archaeologists have discovered hand axes going back at least 130,000 years on the island of Crete, which has been surrounded by the ocean for almost five million years.

The team aims to hunt for additional archaeological sites and reexamine artifact collections that may hold unsuspected traces of human activity in the future.

If people did wander North America 130,000 years ago, they were most likely few in number. This means that discovering human remains is unlikely, but not impossible.