By Alan Boyle Science editor
msnbc.com

Radioactive carbon dating, linguistics and even microscopic analysis of ancient hair are all lending weight to the claim that humans crossed a land bridge from Asia to the Americas many thousands of years earlier than previously thought.

Until recently, the prevailing view was that the first Americans arrived about 11,500 years ago from Siberia, over a land bridge that has disappeared into what is now the Bering Strait. These ancient settlers were called the Clovis people, named after an archaeological find in Clovis, N.M.

But researchers led by University of Kentucky anthropologist Tom Dillehay found human remains and artifacts in Monte Verde, Chile, that have been dated to 12,500 years ago. Although the first discoveries came two decades ago, Dillehay’s scientific critics accepted his findings only last year.

Research presented in February 1998 at the annual meeting of the American Association for the Advancement of Science, indicated that at least two waves of settlers crossed over to the Americas — with the first arriving well more than 20,000 years ago.

Dillehay said charcoal from what could be a fire pit, deep down in the Monte Verde excavation, was dated to 33,000 years ago based on radioactive carbon readings. In light of the 20-year battle over his earlier findings, Dillehay said he wasn’t looking forward to yet another controversy. In fact, he sounded almost regretful over the more recent discoveries.

“I wish it would simply go away,” he said.

Linguistic evidence
Meanwhile, a specialist in linguistics from the University of California at Berkeley said her analysis of scores of languages spoken in the New World led her to conclude independently that the first Americans crossed over surprisingly early.

Professor Johanna Nichols calculated how long it would take a human population to move from Alaska to Chile at an optimum rate — and on that basis turned the clock back to about 19,500 years ago. But at that time, the Bering bridge was thought to have been impassable. “So this speaks to a much earlier entry,” she said.

She also looked at the large number of languages spoken in the New World — about 140 — and said it would require at least 30,000 years to develop such a wide variety. In fact, she said the spread of native languages appeared to indicate that the Clovis people actually came to North America from the south, and not from Siberia. Another wave of immigrants with distinct linguistic characteristics moved across the Bering bridge after ice-age glaciers receded, she said.

Complicated story
Rob Bonnichsen, who directs Oregon State University’s Center for the Study of the First Americans, cited several recent finds that predate Clovis. The Chesrow Complex in Wisconsin contained remains of mammoth bones and stone tools that were dated to 12,000 to 13,000 years ago. At Pendejo Cave in New Mexico, researchers have found and dated a set of fingerprints preserved in clay at least 13,000 years old. And stone points at the Cactus Hills site in Virginia date back 15,000 to 16,000 years, he said.

Oregon State University researchers have developed techniques for analyzing ancient DNA from hair samples found at archaeological sites. The hair can also be carbon-dated, and Bonnichsen said the new techniques should give anthropologists a powerful new tool for linking genetic diversity to the archaeological record.

“We may soon be able to chronicle our own ancestry, but the story is complicated,” he said. “The peopling of the Americas was not a one-issue, one-time event. It was an evolving process involving many different peoples over many periods of time.”

Bonnichsen said a comparison of skeletal features — such as cranial shape and jaw characteristics — supported the view that there was not one prehistoric migration to America, but several.

Smithsonian Institution anthropologist Dennis Stanford said some researchers had been holding back evidence of archaeological finds that predate the Clovis people because of the furor over Dillehay’s results. But now that the Monte Verde findings are widely accepted, Stanford predicted that within the next year there will be even more reports about pre-Clovis Americans.

© 2013 msnbc.com Reprints

Interactive: Language ancestors

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments