Haveyoueverwonderedwhendogsfirstbecame“man’sbestfrie...

问题详情：

    Have you ever wondered when dogs first became “man’s best friend” and the world’s favourite pet? If you have then you’re not alone. When and where dogs first began living side-side with humans are questions that have stirred hot debate among scientists. There are a few hard facts that all agree on. These include that dogs were once wolves and they were the first animal to be domesticated（驯养）by humans. They came into lives some 15000 years ago, before the dawn of agriculture.

    Beyond that, there is little agreement. The earliest bones found that are unquestionable dogs and not wolves date from 14,000 years ago. However, 30,000-year-old skulls have been discovered in France and Belgium that are not pure wolf and some scientists think could be dogs.

    With such puzzling evidence, many scientists are now turning to DNA to find out when and where dogs were first domesticated. In one research project, tens of thousands of blood samples have been taken from street dogs around the world. The plan is to compare them with those of wolves. It’s even possible to analyse DNA from ancient bones. Tiny pieces of the 30,000-year-old skulls mentioned earlier are currently being studied, and another DNA study has already shown that ancient dogs preserved in the Alaskan ice-fields evolved from Asian wolves, not American ones.

    Indeed, the ancient DNA may turn out to be more informative than the DNA of living dogs. Because dogs have accompanied humans around the world for thousands of years, their current distriBution may tell us very little of their origins. This is why different groups of scientists believe that dogs variously originated in eastern Asia, Mongolia, Siberia, Europe or Africa.

    But why were the animals domesticated in the first place? The most recent theory is that dogs domesticated themselves, initially living in and around our ancient villages to eat any food thrown out. Today, this is a way of life still shared by three-quarters of a billion unowned dogs worldwide.

28. Which is the only statement generally agreed on by scientists studying dogs?

originally were used as farm animal

    evolved from wolves found in Europe

    helped the development of agriculture

    were the first animal to be kept as pets

29. Why does the writer first mention the 30,000-year-old animals skulls?

    show that dogs were much larger in the past

    prove that dogs developed from Asian wolves

    suggest that dogs may have evolved much earlier

    argue that dogs were first kept in France and Belgium

30. How did scientists determine the origins of the ancient dogs found in Alaska?

    examining the animals’ DNA       analyzing the age of their bones

    studying the shape of their skulls    comparing them with modern dogs

31. Why did dogs start living with humans?

    use they were attracted by food

    use they were trapped by humans

    use they couldn’t survive in the wild

    use they were trained to protect villages

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DCAA 

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