First posited by the 16th century Spanish naturalist, José de Acosta, it has been a long-standing theory that the indigenous human populations in North and South America arrived there at the end of the last ice age, via the Bering land bridge, before rising ocean levels cut off the connection between the Asian and North American continents. According to this theory, the migrants made their way south via an ice-free corridor that ran between the Cordilleran and Laurentide ice sheets, cutting southward through what is now the province of Alberta in western Canada.
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