Lumps of desiccated feces, dug from a cave in Oregon and stored in plastic bags on a shelf in a science lab, now have some scientists convinced that humans have been in North America for 1,000 years longer than previously thought.
The find turned out to be the oldest directly-dated evidence of human habitation in North America - a 14,300-year- old piece of the puzzle of when we arrived in the New World.
Researchers say the clumps, known as coprolites, were left by Native Americans who were in the region at least 1,000 years before prehistoric tribes known as Clovis people began using their famous spear points to hunt game and carve tools.
Evidence of prehistoric hearths, stone tools and carved bones that are nearly as old have been uncovered in caves and clearings throughout the Americas, including intensively studied sites in Virginia, Pennsylvania and South America.
But the discovery in Oregon's Paisley caves was the first in which scientists were able to pinpoint a date using human DNA. The results were reported yesterday in the online edition of the journal Science.
"We've actually dated human cells to this time period," said Dennis L. Jenkins, an archaeologist at the University of Oregon's Museum of Natural and Cultural History and a member of the international team that published the findings.
Many scientists have thought humans first migrated to North America from Asia by crossing an ice-free corridor in western Canada about 13,500 years ago. They spread out quickly, designing spears and pointed tools they used to hunt to extinction the woolly mammoths, mastodons and other large mammals they found.
But the latest discovery is likely to rekindle debate over how humans first arrived in the Americas. The age of the coprolites indicates that humans were here hundreds of years before the Clovis culture and before the ice-free corridor was formed, experts say.
"The peopling of the Americas is still a big question among scientists," said Fatimah Jackson, a professor of biological anthropology at the University of Maryland. "How did humans first get here, and what were the characteristics of those first people, and how did they survive?"
Scientists found human and canine DNA at the site. To skeptics, that means the human DNA detected by the researchers could have come from people whose remains became mixed in with the feces of earlier animals.
