剑桥雅思7Test3阅读Passage2原文翻译 Population movements and genetics 人口迁移与遗传学
剑桥雅思7阅读第三套题目第二篇文章的主题为人口迁移与遗传学。文章分为7段，分别介绍了人口迁移研究方法的发展，史前美洲人口迁移问题与新线索，通过血液变量分析不同人群之间的关系，三次移民浪潮理论的遗传学依据和牙齿研究证据，以及其他不同的观点。下面是具体每一段的翻译。
点击查看这篇雅思阅读中需要大家掌握的重点词汇以及具体题目的答案解析：
雅思真题阅读词汇 剑桥雅思7 test 3 passage 2 人口迁移与遗传学
剑桥雅思7Test3阅读Passage2答案解析 Population movements and genetics 人口迁移与基因
剑桥雅思7 Test 3 Passage 2阅读原文翻译
段落A
Study of the origins and distribution of human populations used to be based on archaeological and fossil evidence. A number of techniques developed since the 1950s, however, have placed the study of these subjects on a sounder and more objective footing. The best information on early population movements is now being obtained from the ‘archaeology of the living body’, the clues to be found in genetic material.
过去，对人类起源和分布的研究主要建立在考古和化石证据之上。但是，自20世纪50年代以来许多技术的发展使对这些课题的研究拥有了更合理，更客观的基础。现在可以从“活体考古学”（遗传材料中包含的线索）中获得有关早期人口迁移的最佳信息。
段落B
Recent work on the problem of when people first entered the Americas is an example of the value of these new techniques. North-east Asia and Siberia have long been accepted as the launching ground for the first human colonisers of the New World1. But was there one major wave of migration across the Bering Strait into the Americas, or several? And when did this event, or events, take place? In recent years, new clues have come from research into genetics, including the distribution of genetic markers in modern Native Americans2.
关于人们何时首次进入美洲问题的最新研究是这些新技术价值的一个例子。东北亚地区文章来自老烤鸭雅思和西伯利亚地区长期被认为是新世界第一批人类探索者的出发地。但是，是只有一次穿过白令海峡到达美洲的大规模移民浪潮，还是有几次？并且它，或它们是什么时候发生的？近年来，遗传学研究通过现代美洲原住民中遗传标记的分布提供了新的线索。
段落C
An important project, led by the biological anthropologist Robert Williams, focused on the variants (called Gm allotypes) of one particular protein immunoglobin G – found in the fluid portion of human blood. All proteins ‘drift’, or produce variants, over the generations, and members of an interbreeding human population will share a set of such variants. Thus, by comparing the Gm allotypes of two different populations (e.g. two Indian tribes), one can establish their genetic ‘distance’, which itself can be calibrated to give an indication of the length of time since these populations last interbred.
由生物人类学家罗伯特·威廉姆斯主持的重要项目将注意力放在一种人类血液中发现的特定的蛋白质-免疫球蛋白G的变种上。世代之间，所有蛋白质都会“漂移”或产生变体，而相互繁殖的人类种群成员将共享一组此类变体。因此，通过比较两个不同群体的Gm免疫球蛋白（例如两个印度部落），研究人员可以确立他们的遗传“距离”。通过校准，它们可以揭示这些种群上一次互相繁殖的时间。
段落D
Williams and his colleagues sampled the blood of over 5,000 American Indians in western North America during a twenty-year period. They found that their Gm allotypes could be divided into two groups, one of which also corresponded to the genetic typing of Central and South American Indians. Other tests showed that the Inuit (or Eskimo) and Aleut3 formed a third group. From this evidence it was deduced that there had been three major waves of migration across the Bering Strait. The first, Paleo-Indian, wave more than 15,000 years ago was ancestral to all Central and South American Indians. The second wave, about 14,000-12,000 years ago, brought Na-Dene hunters, ancestors of the Navajo and Apache (who only migrated south from Canada about 600 or 700 years ago). The third wave, perhaps 10,000 or 9,000 years ago, saw the migration from North-east Asia of groups ancestral to the modern Eskimo and Aleut.
威廉姆斯和他的同事用了20年的时间在北美西部采集了超过5000名美洲印第安人的血液样本。他们发现他们的Gm免疫球蛋白可以分为两组，其中一组对应中美洲和南美洲印第安人的基因类型。其他测试表明，因纽特人（或爱斯基摩人）和阿留申人组成了第三组。从这一证据可以推断出白令海峡发生了三次大的移民浪潮。15000多年前的第一波Paleo-Indian浪潮构成所有中美洲和南美洲印第安人的祖先。大约12000年到14000之前的第二波浪潮带来了Na-Dene猎人。他们是Navajo和Apache的祖先，600或700年前才从加拿大向南迁移。9000年到10000年前的第三波浪潮见证了现代爱斯基摩人和阿申留人的祖先从东北亚的迁徙。
段落E
How far does other research support these conclusions? Geneticist Douglas Wallace has studied mitochondrial DNA4 in blood samples from three widely separated Native American groups: Pima-Papago Indians in Arizona, Maya Indians on the Yucatán peninsula, Mexico, and Ticuna Indians in the Upper Amazon region of Brazil. As would have been predicted by Robert Williams’s work, all three groups appear to be descended from the same ancestral (Paleo-Indian) population.
其他研究在多大程度上支持了这些结论呢？遗传学家道格拉斯· 华莱士研究了三个广泛分布的美洲本土人群（Arizona的Pima-Papago印第安人，墨西哥Yucatan半岛的玛雅印第安人，以及巴西北部亚马逊地区的Ticuna印第安人）血液样本中的线粒体DNA。正如罗伯特·威廉姆斯的研究所预测的那样，所有三组人群似乎来自同一祖先群体（Paleo-Indian）。
段落F
There are two other kinds of research that have thrown some light on the origins of the Native American population; they involve the study of teeth and of languages. The biological anthropologist Christy Turner is an expert in the analysis of changing physical characteristics in human teeth. He argues that tooth crowns and roots5 have a high genetic component, minimally affected by environmental and other factors. Studies carried out by Turner of many thousands of New and Old World specimens, both ancient and modern, suggest that the majority of prehistoric Americans are linked to Northern Asian populations by crown and root traits such as incisor6shoveling (a scooping out on one or both surfaces of the tooth), single-rooted upper first premolars6 and triple-rooted lower first molars6.
有另外两种研究在某种程度上揭示了美国原住民的起源。他们涉及对牙齿和语言的研究。生物人类学家克里斯蒂·特纳（Christy Turner）是分析人类牙齿物理特性变化的专家。他认为，牙冠和牙根具有很高的遗传成分，很少受环境和其他因素的影响。特纳对成千上万个古代和现代的新旧世界标本进行的研究表明，大多数史前美国人的牙冠与牙床特征与北亚人口存在联系。
According to Turner, this ties in with the idea of a single Paleo-lndian migration out of North Asia, which he sets at before 14,000 years ago by calibrating rates of dental micro-evolution. Tooth analyses also suggest that there were two later migrations of Na-Denes and Eskimo-Aleut.
特纳认为，这与Paleo-India人一次从北亚迁出的想法有关。他通过校准牙齿微观进化的速率将这一时间定在14000年前。牙齿分析还表明，后来存在Na-Denes和Eskimo – Aleut的两次迁移。
段落G
The linguist Joseph Greenberg has, since the 1950s, argued that all Native American languages belong to a single ‘Amerind’ family, except for Na-Dene and Eskimo-Aleut – a view that gives credence to the idea of three main migrations. Greenberg is in a minority among fellow linguists, most of whom favour the notion of a great many waves of migration to account for the more than 1,000 languages spoken at one time by American Indians. But there is no doubt that the new genetic and dental evidence provides strong backing for Greenberg’s view. Dates given for the migrations should nevertheless be treated with caution, except where supported by hard archaeological evidence.
语言学家约瑟夫·格林伯格（Joseph Greenberg）自20世纪50年代以来一直认为，除了Na-Dene和Eskimo-Aleut以外，所有美洲原住民的语言都属于“Amerind”族-这种观点支持三次主要移民浪潮的想法。格林伯格是语言学家中的少数派，其中大多数人都赞成多批次移民浪潮的概念，以解释美洲印第安人同时所讲的1000 多种语言。但是毫无疑问，新的遗传学和牙科证据为格林伯格的观点提供了强有力的支持。但是，除非有确凿的考古证据支持，否则我们应谨慎对待迁徙时间。
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