Week of Feb. 5, 2000; Vol. 157, No. 6

Drowned land holds clue to first Americans
By R. Monastersky

Combining the skills of the late Jacques Cousteau and Louis Leakey, two
Canadian researchers have gone off the deep end to address one of the biggest
questions in anthropology: How did people first make their way to the
Americas? Using sophisticated underwater techniques, the scientists have
mapped out a now-flooded route that could have provided an entry point into
the New World during the last ice age.

"What they're doing is very pioneering. It's a beautiful bit of science,"
comments archaeologist E. James Dixon of the Denver Museum of Natural History.

The Canadian research adds weight to the idea that maritime Asians migrated
down the coast of North America instead of hoofing it overland, as
anthropologists have traditionally believed.

Daryl W. Fedje of Parks Canada in Victoria, British Columbia, and Heiner
Josenhans of the Geological Survey of Canada in Dartmouth, Nova Scotia,
carried out the new study off the coast of the Queen Charlotte Islands, just
south of Alaska. The researchers used high-resolution sonar to complete a
detailed bathymetric map of the underwater landscape.

The chart, published in the February Geology, shows a drowned world of former
river valleys, flood plains, and ancient lakes that would have been above sea
level at the end of the last glacial epoch, more than 10,000 years ago.
During the ice age, so much of the world's water was locked up in continental
glaciers that the height of the oceans dropped by 120 meters. The narrow seas
separating Siberia and Alaska dried up, forming a temporary land bridge
between the two continents.

Using the new map, Fedje and Josenhans went out to collect samples from the
coastal seafloor. They found a pine tree stump and other woody debris that
date to 12,200 years ago, according to the carbon-14 method. This is the
earliest direct evidence that forests had returned to the formerly
ice-covered area. Other sites yielded shells from edible shellfish dating
almost to the same time.

Such clues show how the coastline, which was frozen until about 14,000 years
ago, was growing more hospitable. "At this time, 12,000 years ago, it would
have been a suitable place for people to live and be moving across," says
Fedje.

The researchers also found a stone tool at a location now 53 m below sea
level. They have dated this site to 10,000 years ago, making the tool one of
the earliest human artifacts along the northwest coast of North America.

The new evidence goes against the long-held assumptions of anthropologists
who theorized that the first human immigrants must have been hunters
following mammoths and other large game via an inland route to the North
American Great Plains. Once people passed over the land bridge to Alaska
about 12,000 years ago, according to the older theory, they trekked through a
narrow corridor between two remaining giant ice sheets, one covering
northeast North America and the other blanketing the Rocky Mountains and
their northern extension.

Recently, however, archaeologists have discovered evidence of people reaching
South America by 12,500 years ago, well before the ice-free inland corridor
would have been passable.

"People are looking increasingly toward the coast as an alternative option
for getting to the lower 48 states and other portions of the New World," says
archaeologist David Meltzer of Southern Methodist University in Dallas.
"That's why this kind of [mapping] work is interesting and important, because
it's helping to show us when such routes would have been open, viable, and
possibly traversable."

Meltzer notes, however, that coastal migrants must have arrived well before
the time of the forests documented by Fedje and Josenhans, in order to spread
all the way to the southern end of South America by 12,500 years ago.
Regarding the evidence of human migration, he says, "the further we push it
back, the happier I'll be."

>From Science News, Vol. 157, No. 6, February 5, 2000, p. 85.