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  3. A six-week old infant who died some 11,500 years ago in central Alaska is now providing clues about how the Americas first came

A six-week old infant who died some 11,500 years ago in central Alaska is now providing clues about how the Americas first came

admin2021-12-15  42
问题     A six-week old infant who died some 11,500 years ago in central Alaska is now providing clues about how the Americas first came to be populated.
    Genomic data from remains of the girl—named "Xach’itee’aanenhT’eedeGaay" (Sunrise Girl-Child) by the local indigenous community—broadly support a migration model that scientists have long argued for, while also revealing the existence of an ancient population previously unknown to science. The girl was a member of an ancient population that the report authors have named "Ancient Beringians. " Beringia is the name given to Alaska, Eastern Siberia, and the land bridge that periodically connected the two during the last ice age.
    The findings suggest a revised family tree: a single ancestral Native American group split from East Asians about 35,000 years ago, before later splitting, some 20,000 years ago, into two distinct groups. One was the Ancient Beringians, and the other constituted the ancestors of modern-day Native Americans, who later split into northern and southern populations about 15,700 years ago.
    "Trying to integrate these findings with what we know from archaeology (考古学) and paleoecology (古生态学) presents exciting new puzzles," says Ben Potter, an anthropologist (人类学家) at the University of Alaska. "The peopling has been shown now to be more complex than we thought previously. " Scientists have sought ancient human remains from Beringia at the end of the last ice age, but Xach’itee’aanenhT’eedeGaay’s genome held a surprise: it was clearly Native American, but not from either of the two major modern Native American groups. It represented a population that diverged from that common ancestor.
    All of this helps narrow down and strengthen the theories of just how those populations arrived in the Americas. But mysteries remain, including definitive answers about where and when some of these population splits occurred and which migration routes were used.
    Researchers outline two possible models. In one scenario, which Dr. Potter favors since it matches well with archaeological data and paleoecological data, the split occurred in Northeast Asia, and the two separate populations later crossed over the land bridge prior to 15,700 years ago, when the Native American ancestors split again. In the other theory, the ancestral population had already arrived in Alaska or eastern Beringia by 20,000 years ago, and the split occurred there, with the second split into North and South American populations occurring south of the ice sheets. What happened to the Ancient Beringians? They might have died out, says Potter, or they could have been absorbed by Northern Native Americans who migrated back to the far North.
    Researchers liken the puzzle to a murder mystery. "You read the book, and the author reveals new clues over the course of the book. Every time a new genome is analyzed and reported, it provides a new clue that’s making the pathway to uncover the real story that much clearer. "
What can we learn about the girl called "Xach’itee’aanenhT’eedeGaay"?
选项 A、She was found dead about six-week old some 11,500 years ago.
B、She provided new clues for the study on the first American population.
C、She belonged to an ancient population that used to dwell in Beringia.
D、She migrated to central Alaska sometime during the last ice age.
答案C
解析 由题干中的the girl called“Xach’itee’aanenhT’eedeGaay”定位到原文第二段。推理判断题。本题考查对卡奇媞安妮·媞狄戈伊相关信息的理解。由定位段最后两句可知，这个女孩属于一个名为“古白令人”的古代种群，而这个种群之所以叫这个名称是因为他们居住的地方叫白令，故C)为答案。A)“大约11，500年前她六周大的时候被发现死亡”，该项会产生歧义，原文的意思是她的死亡发生在11，500年前，而非11，500年前她死亡时就被发现了，故排除；B)“她为研究第一个美洲种群提供了新线索”曲解了原文第一段的意思，原文意思是为美洲最初如何开始人口繁衍提供了线索，并非是第一个美洲种群，故排除；D)“她在上个冰河时期的某个时间迁徙至阿拉斯加中部”，从后文可知，她所属的种群有可能进行过这样的迁徙，但不代表她曾如此迁徙过，故排除。
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