2017考研英语《经济学人》文章精选：Seals of doom

  《经济学人》作为考研英语阅读的重要题源，其文章是考研学子重要的阅读材料。从近几年情况看，考研阅读文章一般出自前一年的《经济学人》。因此，聚英考研网精选了《经济学人》中的文章，作为大家考研英语复习的阅读材料。

 

 

  Tuberculosis was first carried to America by pinnipeds

  第一个把结核病带到美国的是鳍足类动物

  When a few intrepid humans crossed the Bering landbridge from the Old World to the New, to populate the Americas 12,000 yearsago, they left many things behind. Among them were several diseases—including smallpox, malaria and tuberculosis—that remained unknown to their descendants until a larger humaninflux began to arrive in 1492. Or rather, in the case of tuberculosis,remained almost unknown. For a few pre-Columbian skeletons bear unmistakablesigns of the infection, creating a mystery that has puzzled anthropologists fordecades.

  Anne Stone of Arizona State University and JohannesKrause of the University of Tübingen nowthink, as they report in Nature, that they have solved this mystery. In doingso they have added a new example to the list of human infections which comefrom wild animals—as Ebola fever, now in the news, camefrom bats and HIV came from chimpanzees. For New World tuberculosis, theysuggest, came from seals.

  Dr Stone and Dr Krause looked for bacterial DNA inthe remains of 68 South Americans who died before Europeans started arriving onthe continent and whose skeletons showed evidence of tuberculosis infection.They found it preserved in three of them—allrecovered from the same valley in Peru. Radiocarbon dating of these skeletonssuggested that their owners had perished between 1028 and 1280.

  One hypothesis about the origin of New Worldtuberculosis is that the first Americans actually did bring a version of thedisease with them, but that the strain was so mild it was later swamped by thevirulent form endemic in Europe. Dr Stone and Dr Krause quickly knocked thatidea on the head. Their samples bear little resemblance to other human strains.They do, however have 76 mutations which match ones found in a form oftuberculosis that infects seals and sea lions. This dovetails nicely with theobservation that most of the evidence for tuberculosis in the pre-ColumbianAmericas seems, like these three skeletons, to come from the coasts of Peru andnorthern Chile, where seals are abundant and were hunted by the locals.

  Where the seals themselves picked up tuberculosisremains to be determined. Their strain resembles one found in mice, and directcross-infection between land-lubbing rodents and aquatic pinnipeds seems implausible.But not, perhaps, impossible. Seals do suffer badly from anotherspecies-jumping terrestrial infection: canine distemper. Truly, the byways ofdisease are convoluted.

  在一万二千年前，当几个勇敢的人越过白令陆桥，从旧大陆来到新大陆美洲大陆，并在这里繁衍生息时，他们也为这片大陆带来了一些东西。其中，就有几种疾病—包括包括天花，疟疾和肺结核—他们的后代一直都不知道，直到他们迎来了1492年大规模的迁移。或者更确切地说，肺结核当时仍旧不为人所知。人类学家对于在哥伦布发现美洲大陆前，那里的一些人体骸骨却出现了受感染的迹象感到很神秘，并整整困惑了几十年。

  亚利桑那州立大学的安妮?斯通和图宾根大学的约翰内斯?克劳斯认为他们已经解决了这个谜团，并且发表在了“自然”杂志上。在研究过程中，他们把人类感染的，来自野生动物的病例--来自于蝙蝠,艾滋病则来自于黑猩猩的—列表又增加了一种新病例—即现在新闻中出现的埃博拉发热。他们认为，这种新的世界肺结核来自于海豹。

  斯通博士和克劳斯博士在六十八具南美人的尸骨上—他们死于欧洲人迁徙到这片大陆之前，并且他们的骸骨表明他们感染了肺结核--找到了病菌的DNA，他们是在这六十八具骸骨--都是在同一个秘鲁的山谷中发现--的其中三具上找到了这种病菌的DNA。这些骸骨在进行放射性碳年代测定后，表明这些南美人死于1028到1280年。

  对于新世界结核病的由来，现在出现了一种假设，即首批美洲人来到这个新大陆时，确实携带着这种病菌的一个变种，但是这种变种很温和，后来就被来自于欧洲地区病的强烈毒性所掩盖。斯通博士和克劳斯博士很快推翻了这个假说。他们的病例与其它人类病毒几乎没什么相似性。他们在研究过程中发现，那些南美人的骸骨中的76种突变基因，与海豹和海狮受到感染后的，某种形式的结核病相匹配。这就很好地契合了他们的观察结果—在美洲的前哥伦布时期发现的，大部分肺结核的证据—就像这些骸骨，似乎都来自于秘鲁和智利北部海岸，而这些海岸地区有大量海豹，而且已遭到了当地人的捕杀。

  这些海豹是从哪里感染上肺结核的还有待发现。它们身上的病毒与在老鼠身上发现的一种很相似，但是，陆生动物和水生鳍足类动物之间产生直接交叉感染似乎令人难以置信。但是，可能也是有可能的。海豹由于受到另一种跨越物种的传染而痛苦不堪，即犬瘟热。诚然，疾病的冷门领域确实让人费解。

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