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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  53
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. "
Researchers compare their study to a murder mystery as they share similarity in________.
选项 A、the way of approaching the truth
B、the need to acquire new clues
C、the analysis of the course of books
D、the pursuit for the real story
答案A
解析 由题干中的a murder mystery定位到原文最后一段。事实细节题。本题考查对研究人员将人类学谜题与谋杀谜案作类比的理解。最后一段指出，阅读有关谋杀谜案的书籍时，作者会在故事的发展进程中透露新的线索，而人类学的这种研究，也是在每次有新的基因被分析和报道出来时提供新的线索，使得通往真相的道路越来越清晰。可见，两者的相似之处在于接近真相的方式，故答案为A)。B)“获取新线索的需要”与原文最后一句所说的通往真相的路径不相关，可见不是作者进行类比的重点，故排除；C)“对书籍进展的分析”与人类学的研究完全没有关系，故排除；D)“对真实故事的追寻”说法过于笼统，故排除。
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