新视野大学英语读写教程听力 第四册 课文 te-07a_new

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[00:00.00]喜欢hxen.net，就把hxen.net复制到QQ个人资料中！Research into Population Genetics
[00:-1.00]While not exactly a top selling book,
[00:-2.00]The History and Geography of Human Genes is a remarkable collection of
[00:-3.00]more than 50 years of research in population genetics.
[00:-4.00]It stands as the most extensive survey to date
[00:-5.00]on how humans vary at the level of their genes.
[00:-6.00]The book's firm conclusion;
[00:-7.00]once the genes for surface features such as skin color and height are discounted,
[00:-8.00]the "races" are remarkably alike under the skin.
[00:-9.00]The variation among individuals is much greater than the differences among groups.
[00:10.00]In fact,there is no scientific basis for theories
[00:11.00]pushing the genetic superiority of any one population over another.
[00:12.00]The book,however,
[00:13.00]is much more than an argument against the latest racially biased theory.
[00:14.00]The prime mover behind the project,Luca Cavalli-Sforza,
[00:15.00]a Stanford professor,labored with his colleagues for 16 years
[00:16.00]to create nothing less than the first genetic map of the world.
[00:17.00]The book features more than 500 maps that show areas of genetic similarity
[00:18.00]— much as places of equal altitude are shown by the same color on other maps.
[00:19.00]By measuring how closely current populations are related,
[00:20.00]the authors trace the routes by which early humans migrated around the earth.
[00:21.00]Result:the closest thing we have to a global family tree.
[00:22.00]The information needed to draw that tree is found in human blood:
[00:23.00]various proteins that serve as markers to reveal a person's genetic makeup.
[00:24.00]Using data collected by scientists over decades,
[00:25.00]the authors assembled profiles of hundreds of thousands of individuals
[00:26.00]from almost 2,000 groups.
[00:27.00]And to ensure the populations were "pure",
[00:28.00]the study was confined to groups that were in their present locations as of 1492,
[00:29.00]before the first major movements from Europe began
[00:30.00]—in effect,a genetic photo of the world when Columbus sailed for America.
[00:31.00]Collecting blood,particularly from ancient populations in remote areas,
[00:32.00]was not always easy;
[00:33.00]potential donors were often afraid to cooperate,
[00:34.00]or raised religious concerns.
[00:35.00]On one occasion,when Cavalli-Sforza was taking blood samples
[00:36.00]from children in a rural region of Africa,
[00:37.00]he was confronted by an angry farmer waving an axe.
[00:38.00]Recalls the scientist:"I remember him saying, ’
[00:39.00]If you take the blood of the children, I'll take yours.’
[00:40.00]He was worried that we might want to do some magic with the blood."
[00:41.00]Despite the difficulties, the scientists made some remarkable discoveries.
[00:42.00]One of them jumps right off the book's cover:
[00:43.00]a color map of the world's genetic variation
[00:44.00]has Africa at one end of the range and Australia at the other.
[00:45.00]Because Australia's native people and black Africans
[00:46.00]share such superficial characteristics as skin color and body shape,
[00:47.00]they were widely assumed to be closely related.
[00:48.00]But their genes tell a different story.
[00:49.00]Of all humans,Australians are most distant from the Africans
[00:50.00]and most closely resemble their neighbors,the Southeast Asians.
[00:51.00]What the eye sees as racial differences
[00:52.00]—between Europeans and Africans,for example
[00:53.00]—are mainly a way to adapt to climate as humans move from one continent to another.
[00:54.00]The same map,in combination with ancient human bones,
[00:55.00]confirms that Africa was the birthplace of humanity
[00:56.00]and thus the starting point of the original human movements.
[00:57.00]Those findings,
[00:58.00]plus the great genetic distance between present-day Africans and non-Africans,
[00:59.00]indicate that the split from the African branch
[-1:00.00]is the oldest on the human family tree.