History of American Immigration A)Ancient peoples only loosely related to modern Asians crossed the Arctic land bridge to settle

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问题                         History of American Immigration
A)Ancient peoples only loosely related to modern Asians crossed the Arctic land bridge to settle America about 15,000 years ago, according to a study offering new evidence that the Western Hemisphere had a more genetically diverse population at a much earlier time than previously thought. The early immigrants most closely resembled the prehistoric Jomon people of Japan and their closest modern descendants, the Ainu, from the Japanese island of Hokkaido, the study said. Both the Jomon and Ainu have skull and facial characteristics more genetically similar to those of Europeans than those of mainland Asians.
B)The immigrants settled throughout the hemisphere, and were in place when a second migration — from mainland Asia — came across the Bering Strait beginning 5,000 years ago and swept southward as far as modern-day Arizona and New Mexico, the study said. The second migration is the genetic origin of today’s Eskimos, Aleuts and the Navajo of the US southwest. The study in today’s edition of the Proceedings of the National Academy of Sciences adds new evidence to help settle one of anthropology’s(人类学)most controversial debates: Who were the first Americans? And when did they come?
C)"When this has been done before, it’s been done from one point of view," said University of Michigan physical anthropologist C. Loring Brace, who led the team of researchers from the United States, China and Mongolia who wrote the new report. "We try to put together more aspects." For decades, anthropologists held that the Americas were populated by a single migration from Asia about 11,200 years ago — the supposed age of the earliest of the elegantly crafted, grooved arrowheads first found in the 1930s in Clovis, N.M. By the end of the 1990s, however, the weight of evidence had pushed back the date of the first arrivals several thousand years. A site at Cactus Hill, near Richmond, may be 17,000 years old. In Chile, scientists discovering a 12,500-year-old settlement at Monte Verde have found evidence of a human presence that may extend as far as 30,000 years. But as the migration timetable went on, additional questions have arisen. The 1996 discovery in Kennewick, Washington, of the nearly complete skeleton of a 9,300-year-old man with "apparently Caucasoid" features stimulated interest in the possibility of two or more migrations — including the possible incoming from Europe.
D)The new study attempted to answer this question by comparing 21 skull and facial characteristics from more than 10,000 ancient and modern populations in the Western Hemisphere and the Old World. The findings provide strong evidence supporting earlier work suggesting that ancient Americans, like Kennewick Man, were descended from the Jomon, who walked from Japan to the Asian mainland and eventually to the Western Hemisphere on land bridges as the Earth began to warm up about 15,000 years ago at the end of the last Ice Age.
E)Brace described these early immigrants as "hunters and gatherers" following herds of mastodon(乳齿象)first into North America, and eventually spreading throughout the hemisphere. Because the North — in both Siberia and Canada — was still extremely cold, only a limited number of people could make the trek(长途跋涉)and survive. So immigration slowed, Brace said, for about 10 millennia(一千年). Then, about 5,000 years ago, agriculture developed on mainland Asia, enabling people to grow, store and carry food in more lonely areas. Movement resumed, but the newcomers were genetically Asians — "distinct racially" from the first wave, Brace added.
F)The second wave spread across what is now Canada and came southward, cohabiting(同居)with the earlier settlers and eventually creating the mixed population found by the Spaniards in the 15th century. While many researchers agree on the likelihood of two migrations, both their timing and origin are matters of dispute. Brace’s team suggests that both movements occurred after the last Ice Age began to moderate between 14,000 and 15,000 years ago.
G)But University of Pennsylvania molecular anthropologist Theodore Schurr said genetic data in American populations suggest that humans may have been in the Western Hemisphere much earlier — 25,000 to 30,000 years ago. This would mean that the first wave came before the "glacial maximum" between 14,000 and 20,000 years ago, when the Ice Age was at its fiercest and "human movement was practically impossible," Schurr said. "Were there people here before the last glacial maximum?" he asked. "The suggestion is ’Yes’".
H)The third wave arose in the American continent around the year 1000, when a small number of Vikings arrived. Five hundred years later, the great European migration began. In some cases, the co-existence of Europeans and Native Americans was peaceful. In other cases, there were cultural clashes, leading to violence and disease. Many people from Africa, however, were bought here against their will to work as forced laborers in the building of a new nation. As early as 1619, slaves from Africa and the Caribbean were brought forcibly to America. Later, 102 English colonists(later referred to as the "Pilgrims")set sail in 1620 on the Mayflower. They landed in Plymouth, Massachusetts. This is generally considered by many to be the "start" of planned European migration! In 1638, just 18 years after the Mayflower, the Swedes began their migration to America. Unlike the Pilgrim Fathers, the Swedes were not religious opponents — they were an organized group of colonizers sent by the Swedish Government to establish a colony in Delaware. In 1655, the colony was lost to the Dutch. In the mid-1840s, a wave of Swedish migration began with the landing of a group of migrant farmers in New York and continued up to World War I.
I)During the colonial era most of the immigrants to the US came from Northern Europe. Their numbers declined during the 1770s, but picked up during the mid-1800s. New arrivals came from several countries, but mostly from Germany and Ireland where crop failures caused many to leave their homelands. Other groups also arrived from the Netherlands, Spain, Italy, the Scandinavian countries, and Eastern Europe.
According to a study, Jomon people’s facial features have more genetic similarities to Europeans’.

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答案A

解析 根据题目中的线索词According to a study,Jomon people’s facial和genetic similarities toEuropealls将本题出处定位到A)段、该段最后1句提到与亚洲大陆人的头骨和面部特征相比,Jomon(绳纹文化时期)的人类和Ainu(阿依努人)在头骨和面部特征上与欧洲人的更具遗传相似性 题干是原文部分细节的再现。
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