英语听力精选进阶版 7248（在线收听）

一项研究结果显示，远在恐龙时代出现的一些病毒仍然在活跃于当代人类的遗传基因里。

至今为止，科学界对基因组的了解仍然处于初级状态，科学家们希望这项研究能够提供有关人类基因渊源的线索。

With only a small part of our genetic material fully understood, scientists have been trying to unravel where most of our DNA came from and what it does. Now researchers from Oxford, New York and Belgium have investigated the genes of 38 mammals – including humans, mice, elephants and dolphins, and they've found that most of them share traces of the same ancient viruses. The work has established that at least one virus infected our common ancestors as long as one hundred million years ago.

The scientists found that these micro-organisms have adapted to stay within their host cell where they have thrived. So within the double helix of our DNA lies not only a legacy of past infections but also a miniature eco-system in which the viruses live on and evolve.

The researchers hope that further work will identify what role these genetic parasites might play. There's no evidence that they cause harm, indeed one ancient virus is known to help in the growth of the placenta. According to the senior author of the study, Dr Robert Belshaw of Oxford University, understanding these survivors from the distant past may provide clues to the early detection of cancers or infections.

Quiz 听力测试

How many mammals did the researchers study in their investigation?

38 species, including humans, mice, elephants and dolphins.

How long ago do the scientists think at least one of the viruses infected our ancestors?

100 million years ago.

Which two words are used in the report to mean a virus?

A parasite and a micro-organism.

Are these ancient viruses harmful to people today?

No. There's no evidence of them being harmful to people.

Glossary 词汇表

to unravel 解开

genes 基因

traces 微量的

to establish 确认

micro-organism 微生物

to thrive 繁荣兴旺

legacy 遗留下来的资产

parasites 寄生虫

placenta 胎盘

to provide clues 提供线索