The Japan Times, October 27, 1997
Scientifically Speaking
By Janet Asimov
Los Angeles Times

America's Ice Age immigrants took West Coast route

When and how did people arrive in the New World? There are legends invented by descendants of those people, and there are stories written by descendants of immigrants from Europe.
Scientific theories, however, are backed by testable evidence, and new research is closing in on both the when and the how.
The time of arrival was once stuck at about 11,500 years ago, the earliest date of the tools used by the hunter-gatherer Clovis people. Then various older sites were discovered. In Alaska, the Mesa site shows that hunters camped on a hill to watch for game and make weapons as early as 11,700 years ago. In the northern Yukon, the three Blue Fish caves contain animal bones and tools that may be at least 16,000 years old, although there's controversy about it. In northeastern Brazil, fractured rocks were dated to 50,000 years ago but now most scientists do not believe the rocks were altered by humans.
On the other hand, different evidence from Brazil last year rocked the world of archaeology. At the Amazon's Monte Alegre, Anna Roosevelt of the University of Illinois and her colleagues found a cave campsite occupied as long ago as 11,200 years B.P. (Before the Present).
This prompted many debates about how people could have zipped down to Brazil from Alaska so quickly, and why their culture was so different from that of the big game hunters farther north. The Amazonians foraged in forests, fished in rivers and painted in the caves.
As the debates continued this year, the news broke that Thomas D. Dillehay of the University of Kentucky and his colleagues found a site where humans lived on the banks of Chinchihuapi Creek in Monte Verde, Chile.
The Monte Verdeans made tentlike homes (one 20 meters long), grilled mastodon and paleo-llama meat at two communal hearths, gathered freshwater mollusks and plants, made excursions to the seacoast or traded for seaweed and pebbles and used medicinal herbs. One small person left a poignant footprint in clay.
Dillehay says the Monte Verdeans had "a much more complex social and economic organization than archaeologists have come to expect of early New World cultures."
Not only that, but the site dates to as early as 12,800 years ago, and there may be even earlier remains!
With the "when" being pushed back, making the "how" a bigger question. How did humans get into the Americas, especially South America, so early?
Massive glaciation covered much of North America in the last ice age. The Laurentide ice sheet expanded to smother even my small island of Manhattan.
Farther west, the Cordilleran ice sheet weighed so heavily on interior British Columbia and the Coast Range mountains that it caused a "significant tilt" in the shorelines beyond, according to Heiner Josenhans of the Canadian Geological Survey and his colleagues. Those shorelines were broader, then, and free of glaciers.
The Josenhans team analyzed seabed cores of the continental shelf of British Columbia. According to radiocarbon dating, the sea level sank as glaciation progressed 18,000 years ago. By 14,000 years ago, the sea level was down 153 meters.
The resulting dry land was a route for human migration from Siberia. According to Scott A. Elias of the University of Colorado, the prehistoric land bridge between Siberia and Alaska was "a huge region covering more than 1.5 million sq. km (about twice the size of Texas)." Scientists call the land bridge and surrounding unglaciated area "Beringia."
Core analysis by Elias and his colleagues shows that much of Beringia was shrub tundra much like that now found on Alaska's North Slope. Herds did not stay there but probably migrated through it "on their way to grassy upland plains."
Some humans may have stayed in Beringia until the waters rose again by 9,500 years ago. (Josenhans points out that "Haida Indian oral history abounds in legends of rapidly rising seas.")
Many immigrants from Siberia, however, probably kept moving on.
The icefree corridor between the Laurentide and Cordilleran ice sheets had sparse vegetation and scanty game for people to use on a trip south. According to Dillehay, the people "may have skirted the Pacific coast on foot or by boat."
The coastal route would explain the early settlements in South America and their fishing-gathering cultures. If the Chilean settlement is 13,000 years or older, it's possible that people had very good reasons for rushing southward. Not only was North America gripped by glaciers, but other catastrophes occurred. Until 13,000 years ago, glacier ice dams periodically broke, releasing catastrophic floods from ancient lakes Missoula, Bonneville and Agassiz. Into modern times, volcanic eruptions covered vast areas of the northwest with suffocating ash.
The coastal route must have been more inviting. It's ridiculous to argue that humans could not have traveled quickly from Alaska to Chile. It doesn't take a very long time for people to walk across the United States. Some of my ancestors did a couple of thousand kilometers of it, pushing handcarts.
Evidence shows that the first people in the Americas were able to travel quickly for far distances, and, Anna Roosevelt says, "to adapt to a broad range of habitats."
Survival is promoted by making productive use of whatever environment you inhabit at the moment, plus the courage to venture onward.
Never underestimate human resourcefulness.