Remains of meals that included seaweed are helping confirm the date of a settlement in southern Chile that may offer the earliest evidence of humans in the Americas.
Researchers date the seaweed found at Monte Verde to more than 14,000 years ago, 1,000 years earlier than the well-studied Clovis culture.
And the report comes just a month after other scientists announced they had found coprolites — fossilized human feces — dating to about 14,000 years ago in a cave in Oregon.
Taken together, the finds move back evidence of people in the Americas by a millennium or more, with settlements in northern and southern coastal areas.
The prevailing theory has been that people followed herds of migrating animals across an ancient land bridge between Siberia and Alaska, and then moved southward along the West coast. Proof has been hard to come by, however. The sea was about 200 feet (60 meters) lower at the time, and as it rose it would have inundated the remains of coastal settlements.
A team led by anthropologist Tom Dillehay of Vanderbilt University reports on the new seaweed study from Monte Verde, Chile, in Friday's edition of the journal Science.
There is a continuous mountain chain along the western side of the Americas, Dillehay explained in a briefing, with thousands of rivers and streams flowing down the mountains to the ocean. This would have encouraged north-to-south migration, he explained, with some groups choosing to turn and follow rivers inland.
Places like the Paisley Caves in Oregon and Monte Verde in Chile are ideal locations for such settlement, he said.
"We really don't know," he added, but genetic and linguistic evidence is beginning to build a fairly strong case that movement was primarily along the coast, he said.
"I tend to think that, even if they came down the coastline, it is a slow process," Dillehay said. "We're just not finding all of the archaeological sites, yet."
Nine species of seaweed and marine algae were recovered from hearths in the ancient settlement, about 500 miles south of Santiago and about 10 miles inland.
Between 20 and 30 people appear to have lived at the site. Other food remains found there include vegetables, nuts, shellfish, an extinct species of llama and an elephantlike animal called a gomphothere.
Some of the seaweed had been chewed, including two types still used by local natives for medical purposes. Other examples were burned, indicating cooking.
Beach stones and other materials were also found at the inland site, Dillehay said, indicating the people at Monte Verde had a stronger coastal tradition than was previously known.
Dillehay said Monte Verde was originally studied several decades ago, but the seaweed remains were only just discovered in a new analysis of recovered materials.
The materials in Oregon and Chile were radiocarbon-dated at 12,500 years ago — which, Dillehay said, translates to between 14,200 and 14,500 calendar years ago.
The research was funded by the U.S. National Science Foundation, Chile's National Fund for Scientific and Technological Development, the National Geographic Society and the University of Chile.