An intriguing new study has presented evidence that the first-known Americans may have arrived earlier than originally believed. However, they weren’t members of Homo sapiens, the progenitor species of all modern humans. According to the research published in the journal Nature, the earliest inhabitants of the North American continent were Neanderthals that landed more than 100,000 years ago — exceeding the accepted arrival date of 15,000 years ago.

Researchers at the Cerutti Mastodon Site in San Diego County, Calif., claimed to have found proof of human-like behavior in a mastodon skeleton buried just below the surface. The skeleton was first unearthed in 1992 by construction workers who were preparing to build the state highway California State Route 54, connecting the interstate to El Cajon. A number of the bones and teeth were broken in such a way that hinted they were struck in a certain manner while the animal was either still alive or freshly-deceased. Some of the breaks were found in sturdy bones that weren’t usually damaged during burial and fossilization. In addition, the injuries were inconsistent with any damage that could have been caused by hungry carnivores or massive herbivores that could have trampled the mastodon. Researchers postulated that what had happened was that the bones and teeth were placed on two stones, being used as makeshift anvils, and then smashed with three stone hammers, reported the WashingtonPost.com.

This explanation is supported by the presence of five large rounded stones near the location of the mastodon skeleton. Measuring eight inches to 12 inches and weighing up to 32 pounds, the researchers claimed that these stones could not have been deposited at the site by any natural means. Since there was only a gentle stream that once occupied where the mastodon skeleton lay, and no evidence of geological forces occurring anywhere near the site, the stones were most likely collected and carried there by hominins. By using Uranium series dating on the bone specimens, the researchers also found that three of them were 131,000 years old, adding or removing 9,000 years.

In spite of their findings, the research team cannot say for certain if Neanderthals did enter North America thousands of years before Homo sapiens did. Although no remains of any other individual were found, Steve Holen, lead author and director of the Center for American Paleolithic Research, stated that they could have arrived by land or by sea. Bison traveled from Asia to North America roughly 135,000 years ago by crossing the Bering Land Bridge, so it’s probable that the Neanderthal could have done the same. Tom Deméré, lead researcher and paleontologist at the San Diego Natural History Museum, echoed the statement. He added that it’s also possible that the visitors died out without leaving behind any descendants. (Related: Neanderthals gave humans the gene for disease)

The research has garnered a wide range of reactions from experts who were not connected to the study.

On the bone fractures, Vance T. Holliday, an archaeologist at the University of Arizona, has said: “They present evidence that the broken stones and bones could have been broken by humans. But they don’t demonstrate that they could only be broken by humans.”

By contrast, Erella Hovers of the Institute of Human Origins at Arizona State University in Tempe has called the evidence “convincing.”

Of their discovery, Deméré has said to UPI.com: “We could be wrong. But people have to be open to the possibility that humans were here this long ago.”

Read up on more scientific discoveries and breakthroughs by visiting Scientific.news.

Sources include:

UPI.com

ArsTechnica.com

WashingtonPost.com

Nature.com