Unexpected Discovery Reveals People Arrived In North America 20,000 Years Earlier Than Previously Thought

Jan Bartek -AncientPages.com - An unexpected archaeological discovery sheds new light on the arrival of the first people in North America. Scientists suggest people reached North America more than 30,000 years ago or simply said, nearly 20,000 years earlier than previously thought.

While studying ancient agricultural practices in the Tehuacan Valley in Mexico, scientists from Iowa State University trying to establish a date for the earliest human occupation of the Coxcatlan Cave in the valley they decided to examine old bones found many years earlier in a cave.

In the 1960s, researchers discovered several rabbit and deer bones in a nearby cave. Andrew Somerville, an assistant professor of anthropology in world languages and cultures, and his team at Iowa State University obtained radiocarbon dates of the animal bones and the results were interesting as they suddenly took Somerville and his colleagues in a different direction with their work.

The date ranges for the bone samples from the base of the cave ranged from 33,448 to 28,279 years old.

Even though previous studies had not dated items from the bottom of the cave, the researchers were not expecting such old ages. The findings add to the debate over a long-standing theory that the first humans crossed the Bering Land Bridge into the Americas 13,000 years ago.

“We weren’t trying to weigh in on this debate or even find really old samples. We were just trying to situate our agricultural study with a firmer timeline,” Somerville said. “We were surprised to find these really old dates at the bottom of the cave, and it means that we need to take a closer look at the artifacts recovered from those levels.”

The findings provide researchers with a better understanding of the chronology of the region. Previous studies relied on charcoal and plant samples, but he says the bones were a better material for dating.

However, questions still remain. Most importantly, is there a human link to the bottom layer of the cave where the bones were found?

Tehuacan Valley in Mexico. Credit: Markus Hoehn - CC BY 3.0

To answer this question, scientists decided to examine the bone samples for evidence of cut marks that indicate the bones were butchered by a stone tool or human, or thermal alternations that suggest the bones were boiled or roasted over fire.

Determining whether the stone artifacts were products of human manufacture or if they were just naturally chipped stones would be one way to get to the bottom of this,” Somerville said. “If we can find strong evidence that humans did in fact make and use these tools, that’s another way we can move forward.”

Not only was this discovery unexpected, but the process of tracking down the animal bones to take samples was more than Somerville anticipated. The collection of artifacts from the 1960s Tehuacan Archaeological-Botanical Project was distributed to different museums and labs in Mexico and the United States, and it was unclear where the animal bones were sent.

After a year of emails and cold calls, Somerville and his collaborator, Isabel Casar from the National Autonomous University of Mexico, had a potential lead for a lab in Mexico City. The lab director, Joaquin Arroyo-Cabrales, agreed to give Somerville and Casar a tour to help search for the missing collection. The tour proved to be beneficial. Among the countless boxes of artifacts, they found what they were looking for.

“Having spent months trying to locate the bones, we were excited to find them tucked away on the bottom shelf in a dark corner of the lab,” Somerville said. “At the time, we felt that was a great discovery, we had no idea it would lead to this.”

Once he located the bones, Somerville got permission from the Mexican government to take small samples – about 3/4 inch in length and 1/4 inch in width – from 17 bones (eight rabbits and nine deer) for radiocarbon dating. If closer examination of the bones provides evidence of a human link, Somerville says it will change what we know about the timing and how the first people came to America.

One of the rabbit bones dated for the study. Credit: Andrew Somerville, Iowa State University

“Pushing the arrival of humans in North America back to over 30,000 years ago would mean that humans were already in North America prior to the period of the Last Glacial Maximum, when the Ice Age was at its absolute worst,” Somerville said.

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“Large parts of North America would have been inhospitable to human populations. The glaciers would have completely blocked any passage over land coming from Alaska and Canada, which means people probably would have had to come to the Americas by boats down the Pacific coast.”

This study is of great significance as we can now understand better when and how people reached North America for the first time. It is a burning question many scientists and the public want to find an answer to.

Written by Jan Bartek - AncientPages.com Staff Writer

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