Earliest Evidence of Humans in the Americas Could ‘Change Everything’ If True

A mastodon skeleton on display in a diorama with a model of a Native American.

When archaeologist Steven Holen and his team recently completed an extensive analysis of mastodon fossils excavated in California, they were shocked by what they discovered.

“The findings went against nearly everything that we have been taught about early human history in North America,” Holen, co-director of the Center for American Paleolithic Research, told Seeker. “Shock and disbelief initially set in, because we knew that our conclusions would be so controversial.”

He was right. A very heated scientific debate is now raging over the team's study, published in the journal Nature. The paper holds that early humans modified the now-extinct large mammal’s bones around 130,000 years ago. That’s 128,508 years before Christopher Columbus began to explore the Central and South American coasts, and some 115,400 years before humans were thought to have entered North America.

The mastodon's remains were initially spotted in late 1992 during routine paleontological mitigation work at a freeway expansion project site managed by the California Department of Transportation. The location, off State Route 54 in San Diego, has since been named the Cerutti Mastodon site in honor of field paleontologist Richard Cerutti, who led the excavation.

Mastodon bones, tusks, and molars were found buried deeply alongside large stone tools, according to co-author Cerutti, Holen, and their colleagues.

“The tools include stone hammers and stone anvils to break bones to enable marrow extraction and/or to acquire raw material for bone and tooth tools,” explained co-author Richard Fullager, a researcher at the University of Wollongong’s Center for Archaeological Science.

Co-author Daniel Fisher, director of the University of Michigan’s Museum of Paleontology, added that the stone tool wielders “very strategically set up a process” to harvest the marrow from the mammoth’s long bones and to recover “dense fragments of bone” for tool production.

Mastodon remains and stones found at the Cerutti Mastodon site.

In 2014, research geologist and co-author James Paces of the US Geological Survey conducted rigorous uranium-series dating of the mastodon fossils and yielded an estimated burial age of approximately 130,000–130,700 years ago.

More recently, he and the rest of the research team — including senior author and archaeologist Kathleen Holen, Steven Holen’s wife — evaluated microscopic damage present on the mastodon fossils and stones. They compared those patterns with marks produced during experimental studies where they used stone cobbles for percussion of large elephant bones. (Modern elephants are distantly related to mastodons, which became extinct 10,000–11,000 years ago.)

The Holens and their international team of nine other scientists say that they ruled out natural or geological reasons for the mastodon bone breakages, stone shapes, and arrangement of the objects at the San Diego site. They even studied other areas where flood events left bone materials redistributed, and could find nothing like what was discovered at Cerutti Mastodon.

When Erella Hovers, head of the Institute of Archaeology at the Hebrew University of Jerusalem, learned about the new findings, her initial reaction mirrored that of Steven Holen.

She told Seeker that she felt “surprised” and that there was “some brow raising.” Nevertheless, she said, she believes that “the conclusions are well supported.”

“The Eurasian archaeological record of the period shows a lot of movement of various hominins [early humans] across continents,” Hovers continued. “It is not too inconceivable that the Americas were also reached, even if not fully colonized, at that time.”

If true, the scenario begs the question: What species of human was in what is now San Diego around 130,000 years ago?

Possible candidates include Homo erectus (aka Upright Man), Neanderthals, Denisovans, and anatomically modern humans from that time.

Recreation of a Neanderthal.

“Anatomically modern humans have not been found so early in northeastern Asia, but it is not totally impossible that they were around and even made it to North America, if the earliest dates for modern humans further south in China prove to be right,” Fullager said. “It seems unlikely — but again, not impossible — that any human species other than ‘cognitively modern humans’ could make the journey by boat.”

“Neanderthals, Denisovans, or some mix of these genetic populations were in southern Siberia, and feasibly in northeastern Siberia, at this time,” he added. “They could have made the journey by land to North America at the right window of opportunity — after temperatures had risen, ice had melted and the sea levels had not yet drowned Beringia [the Bering Land Bridge].”

Regarding the possibility that early humans arrived in the Americas via watercraft, Holen pointed out that there is evidence for early human travels over water. Mariners are thought to have arrived on the island of Crete 130,000 years ago, and human activity on the island of Sulawesi is believed to have occurred 118,000 years ago. It is therefore possible, he said, that early humans “crossed larger bodies of water like the Bering Strait as well.”

Mastodon remains at the Cerutti Mastodon site.

Numerous scientists question these theories and Holen and his team's conclusions concerning the mastodon remains.

“The presence of a Homo population in North America 130,000 years ago is a huge claim, and I can only remain extremely skeptical for the moment,” Bastien Llamas of the Australian Center for Ancient DNA (ACAD) told Seeker.

Alan Cooper conducted a genetic study with Llamas of the early peopling of the Americas and is the director of ACAD.

“Extraordinary claims such as this require extraordinary evidence,” he said, noting that he does not see such evidence in the new paper.

Anthropologist David Meltzer of Southern Methodist University, a leading expert on the colonization of North America, echoed Cooper’s concerns.

“If you are going to push human antiquity in the New World back more than 100,000 years in one fell swoop, you’ll have to do so with a far better archaeological case than this one,” Meltzer said. “Extraordinary claims require extraordinary proof. We have none of the detailed taphonomic [fossil] evidence necessary to support such a grandiose and extraordinary claim.”

Read more at Discovery News