Humans weren't at risk of dying out during the PETM, because we didn't exist.

在古–始极热事件时人类并没有濒临灭绝的危险，因为我们还不存在。

Over the course of the Eocene epoch, the climate slowly began to cool.

在始时期，气候 开始慢慢变冷。

Other residents of Eocene Antarctica probably came from South America as well.

始南极洲的其他居民可能 也来自南美洲。

In the United States, Boverisuchus shows up fully-formed and ready to run in the early Eocene.

在美国，始期，Boverisuchus 已经完全成形并准备好奔跑。

By the late Eocene, practically all of the primates on those continents died out.

到始晚期， 这些大陆上几乎所有的灵长类动都灭绝了。

As a result, our world is warming faster than it did back in the Eocene.

结果，我们的界变暖的速度 比始。

Floristic Region, but their family was clearly much more widespread during the Eocene Epoch.

植区的地区发现，但它们的 要远得多 在始时期广泛存在。

Clearly, Antarctica’s biodiversity took a hit after the Eocene.

，南极洲的生多样性 在始之后受到了打击。

Though the Cretaceous asteroid cleared the stage, mammals did not really get going until 10m years later, in the Eocene epoch.

尽管白垩纪时期的小行星灭绝了居统治地位的恐龙，但哺乳动却一直到1000万年后的始才真正兴起繁盛起来。

But what happened to these Eocene animals?

但是这些始动发生了什么？

What we do know is that the late Eocene and early Oligocene was a time of global cooling.

我们所知道的是，始晚期和 渐期是全球降温的时期。

Around 34 million years ago, the Eocene-Oligocene Transition  marked the first major period of global cooling and glaciation.

大约 3400 万年前，始-渐过渡标志着全球变冷和冰川作用的第一个主要时期。

So given its size, it was able to support many different ecosystems in the Eocene.

所以考虑到它的大小，它能够支持 始许多不同的生态系统。

The Paleocene-Eocene Thermal Maximum, 55 million years ago, was so warm, crocodiles swam the waters of the Arctic Circle.

5500 万年前的古-始极热期非常温暖，以至于鳄鱼在北极圈的水域中游来游去。

So by the time the Eocene Epoch was over, North America no longer had the right habitat for primates.

因此， 当始结束时，北美不再有适合灵长类动的栖息地。

And they arrived in South America by the middle Eocene Epoch, around 42 million years ago.

他们在大约 4200 万年前的始中期到达南美洲。

This period  of warming, known as the Paleocene-Eocene Thermal Maximum or PETM, was likely caused by  a combination of natural factors.

这一变暖时期被称为古-始极热事件或PETM，可能是由多种自因素造成的。

And a big environmental change was also underway in the last half of the Eocene, thanks to the chemistry of mountain-building.

由于造山的化学作用，始后半期也发生了巨大的环境变化。

Antarctica in the Late Eocene, was home to at least two more species of giant penguin.

始晚期的南极洲是至少两种巨型企鹅的家园。

In the early Eocene Epoch, probably before mustelids appeared, our planet had a warm climate.

在始期，可能在鼬动出现之前，我们的星球气候温暖。