(2019·安徽示范高中高三上学期考试)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 by 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 human lives some 15，000 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 wolves’ 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.
【解题导语】 本文是一篇说明文。研究发现，狗是从狼驯养而来的，早在一万五千年之前狗就进入了我们的生活。科学家通过分析DNA去查证狗最初是在何时何地被驯养的。
1．Which is the only statement generally agreed on by scientists studying dogs?
A．Dogs originally were used as farm animals.
B．Dogs evolved from wolves found in Europe.
C．Dogs helped the development of agriculture.
D．Dogs were the first animal to be kept as pets.
D 解析：细节理解题。根据第一段第一句，再结合倒数第二句可知，狗是第一种被人类驯养成宠物的动物，故D项正确。
2．Why does the writer first mention the 30，000－year－old animals’ skulls?
A．To show that dogs were much larger in the past.
B．To prove that dogs developed from Asian wolves.
C．To suggest that dogs may have evolved much earlier.
D．To argue that dogs were first kept in France and Belgium.
C 解析：推理判断题。根据第二段第三句可知，在法国和比利时已经发现了3万年前的头骨，它们不完全是狼的，科学家认为有一些可能是狗的。据此可推知，该处提及三万年前的头骨旨在说明狗的进化历史更早，故C项正确。
3．How did scientists determine the origins of the ancient dogs found in Alaska?
A．By analyzing the age of their bones.
B．By examining the animals’ DNA.
C．By studying the shape of their skulls.
D．By comparing them with modern dogs.
B 解析：细节理解题。根据第三段尾句中的“another DNA study has already shown that ancient dogs preserved in the Alaskan ice fields evolved from Asian wolves, not American ones”可知，科学家是通过检测DNA的方法来判断阿拉斯加狗的起源的，故B项正确。
4．Why did dogs start living with humans?
A．Because they were attracted by food.
B．Because they were trapped by humans.
C．Because they couldn’t survive in the wild.
D．Because they were trained to protect villages.
A 解析：推理判断题。根据尾段第二句可知，最近的一种说法是，狗是自己驯养自己的，最初生活在我们古老的村庄里或周围，吃人们扔掉的食物。据此可推知，狗和人生活在一起的原因是它们被食物所吸引，故A项正确。
