英语听力文摘503 生命的足迹
纳尼!还不对?
那究竟是什么呢?
今天的节目将为您讲述生命的起源……
Life Traces in Lava
Don: Can I ask you something, Ya?l?
Ya?l: Sure!
D: Do you ever stop to think about how all living things are ultimately related?
Y: Eh…Yeah, sure.
D: Bu...but I'm serious. Doesn’t it amaze you to realize that we can trace life back millions and millions of years ago to single-celled organisms floating around in the ocean?
Y: Millions? Actually, it's billions and billions.
D: Billions?
Y: Yes, billion! Scientists have discovered lava rock taken from the ocean floor that contains remnants of life that are billions of years old. Three point five billion years, to be precise.
D: What do they find, fossils?
Y: Sort of. At certain spots the ocean floor oozeslava, which cools and forms rock formations. Microorganisms set up shop on the surface of these rocks and thrive on their rich chemical content. The microbes leave traces of their presence in the rocks in the form of tiny tubes.
When researchers looked at three billion plus year old rocks and saw these kinds of tubes, they suspected that microbes once inhabited them. The most convincing piece of evidence was a type of carbon found in the tubes that’s produced by living things. So far, this is one of the oldest traces of life ever found.
熔岩中的生命足迹
Don: Y 我能问你一个事情吗?
Ya?l: 当然!
D: 你有没有停下来想过人类最初是怎么来的呢?
Y: 额…当然啦!
D: 我认真的!当你意识到人类的起源可以追溯到数百万年前漂浮在海洋里的单细胞生物时，难道你一点也不惊叹于造物的神奇?
Y: 数百万?实际上，应该是“数十亿”吧!
D: 十亿?
Y: 恩，十亿。科学家在海洋底部发现了含有数十亿年前的生物残余的熔岩。准确的说，是35亿年前。
D: 他们发现的是什么?化石?
Y: 好像是。海底的某些地方会渗出岩浆，冷却过后便形成了岩石。微生物便在这些岩石表面“安营扎寨”，靠着岩石中丰富的化学成分生长繁衍。这些微生物在岩石中呈微型管状，留下了他们存在的“足迹”。
当研究人员对这些经历了30多亿年“磨炼”的岩石进行研究时，发现了这些微型的小管，便设想微生物曾经栖居于这些岩石之上。最有力的证据是科学家在这些管状物中发现了一种碳，而这种碳物质仅由生物产生。这是迄今为止发现的最早的生命的“足迹”。
