Earliest Americans' origins traced.

Research discoveries fueled by recent 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. According to Rob Bonnichsen, director of the Center for the Study of the First Americans, Oregon State University, Corvallis, the idea of a single, biological source is dubious because of skeletal, linguistic, archaeological, and genetic evidence to the contrary.

The key to linking the differing strands of evidence may be in a new field of study called molecular archaeology. It is based upon the most common surviving evidence found in archaeological sites--hair. Not only is hair remarkably durable, he points out, it can be quite revealing. Over the last few years, researchers have discovered how to get a radiocarbon date and extract ancient DNA from a single strand of hair about two inches long.

"Hair research opens a whole new door in our search for the first Americans. 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."

Recent archaeological evidence continually is 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 that have been dated at 12-13,000 years old. At Pendejo Cave in New Mexico, a set of fingerprints has been discovered preserved in clay that are at least 13,000...