# Population movements and genetics: answers and explanations

Cambridge IELTS 7, Test 3, Reading Passage 2

Source: Passage, questions and answer key from Cambridge IELTS 7, Test 3, Reading Passage 2. © Cambridge University Press & Assessment. Used for educational practice. Explanations and evidence notes are written by Testmigo.

## Answer key

| Q | Answer | Proof |
| --- | --- | --- |
| 14 | iv | A number of techniques developed since the 1950s, however, have placed the study of these subjects on a sounder and more objective footing. |
| 15 | vii | But was there one major wave of migration across the Bering Strait into the Americas, or several? |
| 16 | x | 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 |
| 17 | i | From this evidence it was deduced that there had been three major waves of migration across the Bering Strait. |
| 18 | vi | As would have been predicted by Robert Williams's work, all three groups appear to be descended from the same ancestral (Paleo-Indian) population. |
| 19 | ii | The biological anthropologist Christy Turner is an expert in the analysis of changing physical characteristics in human teeth. |
| 20 | E | The first, Paleo-Indian, wave more than 15,000 years ago was ancestral to all Central and South American Indians. |
| 21 | D | who only migrated south from Canada about 600 or 700 years ago |
| 22 | C | 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. |
| 23 | B | The second wave, about 14,000-12,000 years ago, brought Na-Dene hunters, ancestors of the Navajo and Apache |
| 24 | A | Pima-Papago Indians in Arizona ... The first, Paleo-Indian, wave |
| 25 | A | Ticuna Indians in the Upper Amazon region of Brazil |
| 26 | A | Studies carried out by Turner of many thousands of New and Old World specimens, both ancient and modern |

## Why these answers are right

**14. iv.** Section A explains how the study of early populations moved from fossil and archaeological evidence to newer techniques developed since the 1950s, especially genetic clues. That change in method matches heading iv, developments in the methods used to study early population movements.

**15. vii.** Section B raises old questions about the first people to enter the Americas: whether there was one wave across the Bering Strait or several, and when it happened. These are long-standing questions about prehistoric migration to America, heading vii.

**16. x.** Section C describes how Gm allotypes in blood are compared between two populations to measure their genetic distance and estimate when they last interbred. That account of the method matches heading x, about measuring how closely related populations are.

The why and the trap for questions 17 onwards are free with an account on the [answers page](https://testmigo.com/ielts/reading/population-movements-and-genetics/answers).

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