Population Movements and Genetics Reading Answers: IELTS Reading Practice Test

Population Movements and Genetics Reading Passage

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Origins and distribution of human populations is studied based on archaeological and fossil evidence. From the 1950s, numerous techniques have been used which are more objective. Information about early population movements now obtained by 'archaeology of the living body', the clues are taken from the genetic material. 

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These values of the techniques are ensured by the work on the problems which deal with when people entered America. The launching ground of human colonisers of the New World is North-east Asia and Siberia. It was found that major migration happened across the Bering Strait into the Americans. New clues have derived from the research into genetics which includes the genetic markers in modern Native Americans. 

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Biological Anthropologist Robert Williams found one particular protein (immunoglobulin G) in the form of fluid in the blood. Most of the proteins produce variants and interbreeding human population members will share these sets of variants. One can determine their genetic distance by comparing the Gm allotypes of two different populations. This informs the length of time. 

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In the span of a twenty year period, Williams and his colleagues collected the sample of over 5,000 American Indians in Western North America. . Gm allotypes can be divided into two groups, one of them corresponds to the genetic typing of Central And South American Indians. Apart from this, other tests showed that Aleut3 and Inuit formed a third group. It was found from the evidence that there have been three migration waves that happened across the Bering Strait. da 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.

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To what extent does other research support these conclusions ? Douglas Wallace, a geneticist, studied mitochondrial DNA4 in the blood samples from three distinct Native American Groups: Arizona’s Pima-Papago Indians, Maya Indians on the Yucatan Peninsula, Mexico, and Ticuna Indians in Brazil's Upper region. According to the prediction of Robert Williams’s work, all three groups seem to be descended from the same ancestor - the Paleo-indian population. 

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There are two other sorts of research which throws some light on the Native American Population origination. It involves the study of teeth and of languages. The biological anthropologist Christy Turner, having an expertise in analysing the changing physical characteristics in human teeth. According to him, tooth crowns and roots possess a high genetic component, affected by environmental and other factors in a minimal fashion. Turner studied many thousands of New and Old World Specimens, both ancient and modern and finds that most of the prehistoric Americans are connected to Northern Asian Populations by root and crown traits such as incisor shovelling ( a scooping out on one or both surfaces of the tooth ), triple-rooted lower first molars and single-rooted upper first premolars.

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As stated by Turner, this ties in with the idea of a single Paleo-Indian migration out of North Asia, which he fixes before 14,000 years ago by calibrating rates of dental micro-evaluation. Analysing the tooth suggests that there were two later migrations of Eskimo-Aleut and Na-Denes. 

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Since the 1950s, the linguist Joseph Greenberg has argued that all Native American languages belong to a single ‘Amerind’ family, Na-Dene and Eskimo-Aleut is an exception - a view that supports the idea of three main migrations. Among fellow linguists, Greenberg is a minority, who favour the idea of many waves of migration to account for the fact that American Indians speak more than 1000 languages at one time. Greenberg’s view is supported by the new genetic and dental evidence. However, dates given for the migrations should be treated cautiously, excluded where supported by hard archaeological evidence. 

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