Pieces of 14,000-year-old poop found in Oregon are the oldest direct evidence of humans in North America, an international team of scientists has announced.
The excrement offers important new DNA evidence about the identity of the first North Americans, say the researchers, who published their findings Thursday in the online edition of the Journal Science.
The 14 feces, or coprolites, were found in the Paisley caves in south-central part of the state by University of Oregon archeologist Dennis Jenkins in 2002 and 2003. He also found tools, and bits of thread, cord and baskets.
It took him a few years to get the feces dated and analyzed.
The oldest piece is 14,300 years old, and the samples contain genetic material that is unique to that of the modern indigenous people of North and South American, says Eske Willerslev, a Danish expert in ancient DNA and one of the authors of the paper. It also is similar to DNA found in modern people in East Asia and Siberia.
This suggests that earliest known North Americans came from Asia and Siberia, he says, and were the ancestors of modern native peoples.
It also counters a number of theories that suggest the first North Americans were close relatives of ancient Australians, Japanese, Pacific Islanders, southern Asians or black Africans.
These theories are all based on the shapes of ancient skulls found in North and South America, but DNA evidence is more convincing that skull morphology, says Dr. Willerslev.
“These are for sure the oldest, direct human remains in North America. The beautiful thing about feces is that you can directly date them, because they are organic.”
The discovery is also another powerful blow to a once-popular theory that the first North Americans were a group of skilled hunters known as the Clovis people. They are believed to have walked across a land bridge between Siberia and Alaska about 13,000 years ago, and left their elegantly carved blades across the United States and Central America.
But starting in the 1970s, archeologists began digging up artifacts were found in Florida, Wisconsin and Chile that were older and didn't have the same distinctive shapes.
The feces found in the Oregon caves offer the most concrete evidence yet that the first people to colonize North America came before the Clovis hunters.
Multiple laboratories dated the feces and analyzed the DNA. In order to be sure they hadn't been contaminated with the DNA of people who had handled the turds, Dr. Jenkins had to chase down all 50 students who had worked on the dig to get a hair sample.
Dr. Jenkins has also analyzed the contents of the ancient feces, and found the earliest North Americans had eaten sage grouse and chipmunk in the 24 hours before they had bowel movements.
