It was the midcontinental corridor between two massive ice sheets—the Laurentide to the west—that enabled the southward migration.
正是两块巨大的冰原之间的半大陆性质的通道——西面的劳伦斯泰德冰原——使人们向南迁移成为可能。
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It was this midcontinental corridor between two massive ice sheets—the Laurentide to the east and the Cordilleran to the west—that enabled the southward migration.
Recent evidence favors a rival to the long-standing theory that the Americas were colonized 11,000-12,000 years ago by people migrating south from Beringia along a midcontinental ice-free corridor.