从西海岸殖民美洲的德芙阅读陪你过七夕

七夕节小编为大家分享一篇托福阅读资料吧！没有情人的节日，其实看看书做做题也是不错的选择哦！

托福阅读文本练习：COLONIZING THE AMERICAS VIA THE NORTHWEST COAST (TPO9)

It has long been accepted that the Americas were colonized by a migration of peoples from　Asia, slowly traveling across a land bridge called Beringia (now the Bering Strait between　northeastern Asia and Alaska) during the last Ice Age. The first watercraft theory about the　migration was that around 11,000-12,000 years ago there was an ice-free corridor stretching from　eastern Beringia to the areas of North America south of the great northern glaciers. It was the　mid-continental corridor between two massive ice sheets-the Laurentide to the west-that enabled　the southward migration. But belief in this ice-free corridor began to crumble when paleoecologist　Glen MacDonald demonstrated that some of the most important radiocarbon dates used to　support the existence of an ice-free corridor were incorrect. He persuasively argued that such an　ice-free corridor did not exist until much later, when the continental ice began its final retreat.

Support is growing for the alternative theory that people using watercraft, possibly skin boats,moved southward from Beringia along the Gulf of Alaska and then southward along the Northwest　Coast of North America possibly as early as 16,000 years ago. This route would have enabled　humans to enter southern areas of the Americans prior to the melting of the continental glaciers.

　　Until the early 1970s, most archaeologists did not consider the coast a possible migration route　into the Americans because geologists originally believed that during the last Ice Age the entire　Northwest Coast was covered by glacial ice. It had been assumed that the ice extended westward　from the Alaskan/Canadian mountains to the very edge of the continental shelf, the flat,submerged part of the continent that extend into the ocean. This would have created a barrier of　ice extending from the Alaska Peninsula, through the Gulf of Alaska and southward along the　Northwest Coast of North America to what is today the state of Washington.

　　The most influential proponent of the coastal migration route has been Canadian　archaeologist Knut Fladmark. He theorized that with the use of watercraft, people gradually　colonized unglaciated refuges and areas along the continental shelf exposed by the lower sea level.Fladmark's hypothesis received additional support from the fact that the greatest diversity in　Native American languages occurs along the west coast of the Americans, suggesting that this　region has been settled the longest.

　　More recent geologic studies documented deglaciation and the existence of ice-free areas throughout major coastal areas of British Columbia, Canada, by 13,000 years ago. Research now　indicates that sizable areas of southeastern Alaska along the inner continental shelf were not　covered by ice toward the end of the last Ice Age. One study suggests that except for a 250-mile　coastal area between southwestern British Columbia and Washington State, the Northwest Coast　of North America was largely free of ice by approximately 16,000 years ago. Vast areas along the　coast may have been deglaciated beginning around 16,000 years ago, possibly providing a coastal　corridor for the movement of plants, animals, and humans sometime between 13,000 and 14,000　years ago.

　　The coastal hypothesis has gained increasing support in recent years because the remains of　large land animals, such as caribou and brown bears, have been found in southeastern Alaska　dating between 10,000 and 12,500 years ago. This is the time period in which most scientists　formerly believed the area to be inhospitable for humans. It has been suggested that if the　environment were capable of supporting breeding populations of bears, there would have been　enough food resources to support humans. Fladmark and others believe that the first human　colonization of America occurred by boat along the Northwest Coast during the very late Ice Age,possibly as early as 14,000 years ago. The most recent geologic evidence indicates that it may have　been possible for people to colonize ice-free regions along the continental shelf that were still　exposed by the lower sea level between 13,000 and 14,000 ago.

　　The coastal hypothesis suggests an economy based on marine mammal hunting, saltwater　fishing gathering, and the use of watercraft. Because of the barrier of ice to the east, the Pacific　Ocean to the west, and populated areas to the north, there may have been a greater impetus for　people to move in a southerly direction.

　　以上就是小编今天为大家整理的一篇托福阅读资料，除了以上资料外，小编这里还有很多精华版的托福阅读备考资料，例如OG、TPO、真题等等，想要这些资料的考生可以关注成都新航道获取哦。

 【推荐阅读】

在托福听力中如何正确的抓取重点词汇

你吃过“冰淇淋”吗