The long-ago seas of the Carboniferous and Devonian swarmed with tiny plankton that wrapped themselves inside tiny protective shells.

石炭的古代海洋里生活着大批微小的浮游生。它们躲在小小的保护性壳里。

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4亿年以前的寻找。

Well, during the Devonian, things were … complicated.

好吧，在期间，事情… … 很复杂。

Going back even further, we find the Late Devonian extinction about 360 million years ago.

再往前追溯， 我们发现大约 3. 6 亿年前的晚世大灭绝。

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

但这些生生活在 与截然不同的世界中。

The Ordovician (440 million years ago) and Devonian (365 million) each wiped out about 80 to 85 percent of species.

奥陶（44000万年以前）（36500万年以前）分别消灭了大约80%——85%的种。

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，但它们在大量繁殖。

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， 在时期，四足动开始冒险离开水边。

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

但在，出现了头足类 家族树的一个新分支：菊石。

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，尤其是在拥挤的海域。

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

一旦植生命在时期开始在陆地上传播多样化，真菌就会再次提供帮助。

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的种灭绝，它发生在两次主要的爆发中。

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

海洋中栖息着这些种的动，并将成千上万的它们沉积在较新地层的岩石中。

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石炭，空气中的氧的浓度高达35%（现在是将近20%）。

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

这些植中的木材直接导致了发生的大量土壤生成。

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

因为，在的这个时候，抓住水是一个真正的挑战。

Take, for example, that plant I mentioned  earlier: Archaeopteris from the late Devonian.

以我之前提到的植为例：晚期的古蕨属。

So armored fish came in a variety of shapes and sizes during the Silurian and Devonian, from tiny Heterostracans to massive Placoderms.

因此，在志留期间， 装甲鱼的形状大小各不相同，从微小的异类鱼到巨大的盾皮鱼。

When they first appeared in the Early Devonian, the fungal spires of Prototaxites towered over everything else that grew, burrowed, and crawled around them.

当它们第一次出现在早世时，原杉藻类的真菌尖顶高耸于所有在它们周围生长、挖洞爬行的植之上。

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

到末期，植已经发展出它们茁壮成长所需的几乎所有特征。