Debate over the Earliest Route to the Americas

Laurentide Ice Sheet

Approximate coastline ¦ during maximum " ¦ , glacial extent i

Scientists have determined that many of the oldest skeletons in the Americas were genetically similar to ancient skeletons found in the Lake Baikal region of Siberia. Scholars hypothesize that about 30,000 years ago people from the Baikal area moved north and east, likely in pursuit of big mammals, and eventually crossed the Bering Strait to Alaska. This was during the last ice age, when so much water had been captured as glacial ice that ocean levels were hundreds of feet lower than they are today. These roaming hunters did not know they had entered a new continent.

As they reached what is now Fairbanks, Alaska, they came upon the massive Cordilleran Ice Sheet and, farther east, the Laurentide Ice Sheet. That early peoples could have made their way across so formidable an obstacle, or would even have wished to do so, seems doubtful.

Until recently, most scholars believe that around

12,000 years ago, global warming melted enough of the

Between the two—an ice-free corridor leading to present-day Calgary and the Great Plains. The discovery of advanced hunting blades and skeletons at Clovis, New Mexico, dating from around this period, seemingly confirmed this thesis.

But during the past decade, human skeletons older than this have been found in the Americas:Those in Meadowcraft, Pennsylvania, in Cactus Hill, Virginia, and in Topper, South Carolina, presumably date from around

16,000 BP (before the present) or earlier. Most puzzling is a site containing evidence of human occupation in Monte Verde, Chile, which some archaeologists date from 30,000 BP.

If the ice-free corridor from Alaska had not opened until 13,000 BP, how did peoples get to Pennsylvania, Virginia, South Carolina, and southern Chile thousands of years earlier?

In recent years, some scholars propose that there have been multiple migrations from Asia into the Americas, perhaps the first as early as 30,000 years ago. Nearly everyone agrees that the ice sheets of Canada would have been impassable, but the discovery of ancient skeletons along the Pacific coast has given rise to the thesis that the first Paleo-Indians made their way down the Pacific coast. This conclusion is strengthened by DNA analysis that suggests that

Paleo-Indian bones along the Pacific coast were from a different population pool of Paleo-Indian bones found in the Midwest and the eastern United States. The chief problem with the theory—the relative absence of much evidence of early human habitation—is explained by the fact that these earliest Americans would have traveled along coastal routes that were subsequently flooded as global warming raised the level of the Pacific Ocean.

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