PHILADELPHIA - New research discoveries fueled by technological advancements strongly suggest that the earliest inhabitants of the North American continent not only arrived much earlier than once believed, but that they may have originated from different biological and geographical backgrounds.
This new model of "First American" studies was presented Monday in Philadelphia at the annual meeting of the American Association for the Advancement of Science by Rob Bonnichsen of Oregon State University.
Bonnichsen said the idea of a single, biological source for the first Americans is dubious because of skeletal, linguistic, archaeological and now genetic evidence to the contrary. Previous "Clovis models" determined that the Americas were populated about 11,500 years ago by a group of people from eastern Siberia who crossed the Bering land bridge during the last ice age.
"The time lines for populating the continent based on linguistic or genetic models don't match the time scales suggested by skull evidence or the archaeological record," said Bonnichsen, who directs the Center for the Study of the First Americans based at OSU. "And none of them match Clovis. I think we can finally put a nail in the Clovis coffin."
Bonnichsen said the key to linking the differing strands of evidence may be in a new field of study he calls "molecular archaeology." Pioneered at Oregon State University, the field is based upon the most common surviving evidence found in archaeological sites - hair.
Hair is not only remarkably durable, he said, it also can be quite revealing: In the couple of years, researchers have discovered how both to get a radiocarbon date and extract ancient DNA from a single sample of hair just 5-7 centimeters long.
"Hair research opens a whole new door in our search for the first Americans," Bonnichsen said. "It is located in nearly every archaeological site and through DNA analysis can link genetic diversity to the archaeological record. We may soon be able to chronicle our own ancestry, but the story is complicated. 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 also provided details of recent archaeological evidence that is continually pushing back the dates of the earliest entry onto the continent. Among the findings:
- Researchers in Wisconsin working at a series of sites called the Chesrow Complex have found numerous remains of mammoth bones in association with stone tools. They have been dated at 12,000 to 13,000 years old.
- At Pendejo Cave in New Mexico, researchers have found and dated a set of fingerprints preserved in clay that are at least 13,000 years old.
- In Virginia, at a site called Cactus Hills, archaeologists have found lanceolate or "atalatl" points dating back 15,000 to 16,000 years.
All of these early dates are significant, Bonnichsen said, because they pre-date not only the 11,500 year-old date suggested by the Clovis model, but they occur before the Bering land bridge existed. The widespread geographic diversity of the sites - Wisconsin, New Mexico and Virginia - also intrigues scientists, many of whom believe the Americas either were populated several thousand years earlier to achieve such widespread habitation, or that there were multiple points of entry.
Bonnichsen said many linguists involved in first American studies believe there are three different lineages through which early Americans can be traced. The Eskimo-Aleut group occupied the northernmost sections of North America; the Na-dene (NAH-den-AY) were just south of the Eskimo-Aleuts; and American Indians populated the area south of the ancient ice sheets.
New skeletal information - which looks at such features as cranial shape, orbital socket size and jaw characteristics - also suggests that early Americans did not have "a single foundation," Bonnichsen said. The slim skeletal record dating back 10,000 years or so includes remains that most closely resemble Ainu and people of Nordic descent.
The few remains that date back that far "don't physically look at all like modern Native Americans," Bonnichsen said.
"We're at a stage where we really don't know the answers about where people came from and when," Bonnichsen said. "We have a lot of different strands of evidence that don't always seem to fit together. The DNA evidence from hair may be the key we've been missing in our attempts to link the biological evidence to the archaeological evidence."
Researchers affiliated with the Center for the Study of the First Americans first extracted ancient DNA from hair in 1995. Since then, OSU geneticists Kate Field and Walt Ream have refined their techniques and now are able to use much smaller hair samples - about 3-5 centimeters - usually leaving enough of the hair to get a carbon date from it.
The researchers have checked the validity of their method numerous times, even consulting with DNA experts in the Federal Bureau of Investigation, Bonnichsen said.
"Now what we need to do is to identify more archaeological sites, carefully excavate them, and use this new technology to examine human and animal hair that we find," Bonnichsen said. "Hopefully, we will be able to take archaeology and the search for the first Americans to the next level."