时差N小时 寻找地球上最古老的生命(上)（在线收听）

They know by studying the remains of past life preserved in rocks, particularly sedimentary rocks.

研究人员在研究岩石特别是沉积岩中保存着的生物遗骸时找到了证据。

These rocks are formed from particles of mud and sand, typically when they settle to the bottom of a body of water.

这些岩石是由泥土和沙砾沉积在水底形成的。

Fossils of organisms with hard body parts don't appear in sedimentary rock older than about 600 million years,

生物体中较硬的身体部分所形成的化石不会出现在6亿年以上的沉积岩中，

but the Earth itself is 4.6 billion years old.

但是地球预计已经有46亿年之久了。

To find the oldest life, paleontologists looked for it in the oldest sedimentary rock they could find.

为了寻找最古老的生命，古生物学者找到了他们可以找到的最古老的沉积岩。

Sedimentary rocks dating back to Earth's earliest days are rare.

这些可以追溯到形成于地球初期的沉积岩是十分罕见的。

Some of the oldest known are about three and a half billion years old.

目前所知的一些最古老的沉积岩大约有35亿年的历史。

Did they find anything?

他们有什么发现吗？