Excavations on an Army base in southeastern New Mexico have provided dramatic new evidence that humans may have lived on the North American continent for at least 36,000 years, more than three times as long as many researchers now believe, a Massachusetts researcher said Wednesday.
Although other archeologists have reported evidence for such early colonization of the Americas, Richard MacNeish of the Andover Foundation for Archaeological Research said the new site--a cave--provides the most convincing evidence yet.
MacNeish uncovered a veritable condominium of human history--24 levels, complete with fireplaces, ranging from 39,000 years old on the first floor to 10,000 years old at the top. The site was dated by scientists from UC Riverside and UCLA.
Among the evidence extracted from the cave is the 24,000 year-old toe bone of a horse with an arrow point embedded in it and a clay fireplace, complete with what appears to be a human thumbprint, dating from 36,000 years ago.
"This is the earliest well-documented site in America," MacNeish said in a telephone interview. "We have found the first American Indian."
If the new date for man's arrival on the continent is correct, it means that humans would have traversed the Bering Strait from Asia under very severe climatic conditions--when the world was in an ice age. That suggests that early humans were an exceptionally hardy species able to cope with a broad range of adversity.
It also means that humans would have occupied North America during a period of at least 15 centuries in which sheets of ice extended over much of the continent, producing conditions grossly different than those of 12,000 years ago.
But the claim is likely to undergo severe criticism and intensive analysis before it is broadly accepted, other researchers said. Archeologists are sharply divided over when North American colonization occurred.
"This is one of the great controversies in science," according to archeologist Brian Fagan of UC Santa Barbara. "It raises great passions and lots of people don't speak to each other."
"It's something that at least half the archeologists in America will resist, despite the fact that MacNeish has excellent credentials," said anthropologist Russell Barber of Cal State San Bernardino.
The new site is 14 miles east of Orogrande, N.M., on the McGregor Firing Range, part of the Ft. Bliss (Tex.) Military Reservation. MacNeish was digging in the cave looking for pollen and other plant remains because of his interest in documenting the beginnings of agriculture in the Southwest.
"But when we got about a meter down, we began to hit extinct animal bones," he said. The researchers subsequently excavated 24 different floors, each distinguished by burned charcoal from the fire pits. "The stratigraphy is as (convincing) as anyone has dug anywhere," he said.
"The bottom 14 floors have extinct animals, including horses, camels, tapirs, llamas, and dire wolves," he noted. Among the 24 levels, each of which is separated by two to five inches of dust and dirt, they have found 11 hearths, apparently dug by humans.
"We have checked the logs in them and four have logs more than four inches in diameter," indicating they were too big to have been brought in by animals, he said.
The clay lining appears to bear a human thumbprint, he said. The researchers have sent a copy of it to the Royal Canadian Mounted Police forensics laboratory to determine whether it is a human print, he said.
MacNeish and his colleagues have also found 275 artifacts that they believe to be tools used by the early inhabitants of the cave. "Of the 200, 90 are of foreign materials (from outside the cave), some from geological formations more than 10 miles away," he said.
Before MacNeish's discovery, the most convincing evidence for early colonization of North America came from the Meadowcroft Rockshelter near Pittsburgh, which might have been occupied more than 19,600 years ago. Other sites in Mexico and Chile have been reported to be as much as 33,000 years old, but many archeologists remain unconvinced of their authenticity.
It seems likely that MacNeish's results will be similarly challenged. "That's the way the scientific game is played," said geographer Ronald Dorn of Arizona State University, who has himself reported early habitation in the Southwest. "It's just good clean fun."