The clue to this ancestor, it was assumed, would be found in the Devonian era, from about 400 million years ago.

据认为，这个祖先的线索要在大约4亿年以前的泥盆纪寻找。

Well, during the Devonian, things were … complicated.

好吧，在泥盆纪期间，事情… … 很复杂。

But these creatures lived in a very different world from the Devonian.

但这些生物生活在 与泥盆纪截然不同的世界中。

While fish with jaws first appeared in the Silurian, they proliferated in the Devonian.

虽然有颚的鱼最早出现在 志留纪，但它们在泥盆纪大量繁殖。

But in the Devonian, a new branch of the cephalopod family tree appeared: ammonites.

但在泥盆纪，出现了头足类 家族树的一个新分支：菊石。

That's because a new evolutionary pressure was waiting for cephalopods in the Devonian Period: fast, jawed fish.

那是因为在泥盆纪时期，一种新的进化压力正在等待头足类动物：快速的有颌鱼类。

Because, at this point in the Devonian,   holding onto water was a real challenge.

因为，在泥盆纪的这个时候，抓住水是一个真正的挑战。

But about 385 million years ago, in the Devonian Period, tetrapods started venturing away from the water's edge.

但大约 3.85 亿年前， 在泥盆纪时期，四足动物开始冒险离开水边。

It's not really clear what caused the Devonian extinctions, which occurred in two main bursts.

目前还不清楚是什么导致了泥盆纪的物种灭绝，它发生在两次主要的爆发中。

Oxygen levels in the Devonian and Carboniferous periods, when terrestrial life first bloomed, were as high as 35 percent (as opposed to nearer 20 percent now).

在陆地生命大幅度增加的泥盆纪和石炭纪，空气中的氧的浓度高达35%（现在是将近20%）。

By the end of the Devonian period, plants had developed almost all of  the traits they would need to thrive.

到泥盆纪末期，植物已经发展出它们茁壮成长所需的几乎所有特征。

But things started to change about a  quarter of the way into the Devonian Period.

但在进入泥盆纪的大约四分之一时，情况开始发生变化。

The Devonian seas were peopled by animals of these species, and deposited them by thousands in the rocks of the newer formation.

泥盆纪海洋中栖息着这些物种的动物，并将成千上万的它们沉积在较新地层的岩石中。

And the evolution of armor may seem like an obvious adaptation for protection, especially in the Devonian's crowded seas.

盔甲的进化似乎是对保护的明显适应，尤其是在泥盆纪拥挤的海域。

The Devonian is often known as " The Age of Fishes" - the time when things like Dunkleosteus ruled the waves.

泥盆纪通常被称为“鱼类时代”——邓氏鱼等生物统治海浪的时代。

Once plant life started to spread and diversify on land in the Devonian Period, fungi were there to help again.

一旦植物生命在泥盆纪时期开始在陆地上传播和多样化，真菌就会再次提供帮助。

By the end of the Devonian, all of the giant marine eurypterines had gone extinct.

到泥盆纪末期，所有巨大的海洋广翅目动物都灭绝了。

And the wood in these plants was  directly responsible for a lot of the soil generation that  took place in the Devonian.

这些植物中的木材直接导致了泥盆纪发生的大量土壤生成。

Fish began their transition onto land 400 million years ago, during in the Devonian period.

4 亿年前，在泥盆纪时期，鱼类开始向陆地过渡。

So, while they helped end  the world of the Devonian, if it wasn't for them, our world  might not have gotten started.

因此，虽然他们帮助终结了泥盆纪世界，但如果不是他们， 我们的世界可能就不会开始。