笔译二级实务（综合）模拟试卷34
必做题
1. Modern humans evolved somewhere in Africa roughly 200,000 years ago. But how did our species go on to populate the rest of the globe? Did humans flood out of Africa in a single diaspora, or did we trickle from the continent in waves spread out over tens of thousands of years? The question, one of the biggest in human evolution, has plagued scientists for decades.
Now they may have found an answer.
In a series of unprecedented genetic analyses published on Wednesday in the journal Nature, three separate teams of researchers conclude that all non-Africans today trace their ancestry to a single population emerging from Africa between 50,000 and 80,000 years ago.
Each team of researchers used sets of genomes to tackle different questions about our origins, such as how people spread across Africa and how others populated Australia But all aimed to settle the question of human expansion from Africa
In the 1980s, a group of paleoanthropologists and geneticists began championing a hypothesis that modern humans emerged only once from Africa, roughly 50,000 years ago. Skeletons and tools discovered at archaeological sites clearly indicated the existence of modern humans in Europe, Asia and Australia.
Early studies of bits of DNA also supported this scenario. Yet there are also clues that at least some modern humans lived outside Africa well before 50,000 years ago, perhaps part of an earlier wave of migration.
In 2011 Eske Willerslev, a renowned geneticist at the University of Copenhagen, and his colleagues reported evidence that some living people descended from this early wave.
Willerslev and his colleagues reconstructed the genome of an aboriginal Australian from a century-old lock of hair kept in a museum—the first reconstruction of its kind. The DNA held a number of peculiar variants not found in Europeans or Asians.
He concluded that the ancestors of Aboriginals split off from other non-Africans and moved eastward, eventually arriving in East Asia 62,000—75,000 years ago. Tens of thousands of years later, a separate population of Africans spread into Europe and Asia.
It was big conclusion to draw from a single fragile genome, so Willerslev decided to contact living Aboriginals to see if they would participate in a new genetic study. He joined David Lambert, a geneticist at Griffith University in Australia, who was already meeting with aboriginal communities about beginning such a study.
Their new paper also includes DNA from people in Papua New Guinea All told, the scientists were able to sequence 83 genomes from aboriginal Australians and 25 from people in Papua New Guinea.
Meanwhile, Mait Metspalu of the Estonian Biocentre was leading a team of 98 scientists on another genome-gathering project. They picked out 148 populations to sample, mostly in Europe and Asia, with a few genomes from Africa and Australia They sequenced 483 genomes at high resolution.
David Reich, a geneticist at Harvard Medical School, and his colleagues assembled a third database of genomes from all five continents. The Simons Genome Diversity Project, sponsored by the Simons Foundation and the National Science Foundation, contains 300 high-quality genomes from 142 populations.
Reich and his colleagues probed their data for the oldest
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