By Land or Sea?
Between about 25,000 and 10,000 years BP, much of the North American continent was buried beneath tonnes of glacial ice. How did people find their way across or around this massive barrier to settle in the unglaciated regions south of the ice sheets? Which route did they take to travel to the Americas? A number of hypotheses have been proposed to answer these questions, from the plausible to the preposterous, but the ice-free corridor route and the coastal route are the two that have garnered the widest acceptance within the archaeological community.
Proponents of the ice free corridor hypothesis argue that the first North Americans were big-game hunters who followed herds of bison and mammoth from Siberia across the Bering Land Bridge and down an unglaciated inland route east of the Rocky Mountains, to the mid-continent region. Coastal route advocates, on the other hand, suggest that people migrated by boat down the Pacific Northwest coast, inhabiting small pockets of unglaciated land along the outer coast, and relying on marine resources such as fish, shellfish and sea mammals.
There is not yet enough evidence to prove that one or the other of these hypotheses is correct. No archaeological sites have been found in either of these regions that can definitely be linked to the arrival of the earliest people on the continent. Archaeologists continue to search for these early sites, but also rely on evidence from other researchers to determine whether these ancient environments were habitable and capable of supporting plants, animals and people. Geologists, for example, can determine the characteristics of the past physical environment, including the location of coastlines and the presence and extent of ice sheets and glacial lakes. Paleobiologists study ancient plant and animal remains to establish the type of climate and vegetation that people might have encountered, as well as to identify possible food sources for human populations. This research can be used to identify environments that people could have lived in, as well as those that were uninhabitable, and can assist archaeologists in determining where to look for archaeological remains.