ModernEuropeanscamefromthreemajorgroupsofancienthumans,...

问题详情：

Modern Europeans came from three major groups of ancient humans, not two as was thought before, according to a study published on Wednesday.

Until now, it was widely believed that Europeans evolved (进化) from two prehistoric groups. One was early farmers who moved into Europe from the Middle East about 7,500 years ago. The other was local hunter-gatherers who had lived in Europe for more than 40,000 years.

But a new study in the journal Nature says there was a third group in the mix: people from northern Eurasia. They lived in today’s Russia and northern Asia. The finding means that northern Eurasians contributed to the human genes (基因) both in Europe and North America.

Their influence on the Americas has been proved by previous studies which showed that they reached modern-day Alaska in the US more than 15,000 years ago. They crossed an “ice bridge” that connected islands in the Bering Strait, a narrow passage of water between Asia and North America, at the time.

Researchers collected genetic information in nine ancient humans’ bones. The remains were found in Sweden, Luxembourg and Germany. They were one farmer from about 7,000 years ago and eight hunter-gatherers who lived about 8,000 years ago, before the coming of agriculture.

The researchers compared the information with the gene pool of 2,345 present-day people living all over the world. They found almost all Europeans have ancestry from all three of those ancient groups.

The ancient northern Eurasians contributed up to 20% of the genetics of Europeans, although this was the smallest percentage among the three ancestral groups.

People in northern Europe, especially the Baltic states, have the highest percentage of western European hunter-gatherer ancestry. Up to 50% of the DNA of Lithuanians of northeast Europe comes from this group.

Southern Europeans had more of their genetic ancestry from the ancient farmers. Up to 90% of the DNA of Sardinians of Italy can be traced back to (追溯到) these early European immigrants.

Looking ahead, the researchers plan to find out when the ancient northern Eurasians arrived in Europe.

13. Ancient people from northern Eurasia _____.

A. brought agriculture into Europe                      B. reached Europe about 7,000 years ago

C. were hunter-gatherers in northern Asia           D. were also ancestors of modern Europeans

14. When did northern Eurasians arrive in America?

A. About 7,500 years ago.                                 B. About 8,000 years ago.

C. More than 15,000 years ago.                         D. More than 40,000 years ago.

15. How did the researchers conduct the study?

A. By analysing genes.                                      B. By visiting ancient sites.

C. By doing medical experiments.                       D. By comparing studies in different periods.

16. What do “these early European immigrants” refer to?

A. Hunter-gatherers in western Europe.                     B. Hunter-gatherers in northern Europe.

C. Ancient farmers from the Middle East.            D. Ancient farmers from northern Eurasia.

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