Nobody knows quite how the Spanish overcame thisproblem

没人知道西班牙移民如何征服了这个困难

but it's probably no more complicated than havingchildren with the locals.

可能是西班牙人和当地人结婚生子

Even Andean peoples wouldn't be able to live permanently above 5,000 metres.

甚至安第斯人也无法在五千米环境生活

Higher than this and human reproduction is impossible.

高于这一海拔人类难以生育

In other words, oxygen sets a limit on the very existence of our species.

换句话说，氧气对于我们的物种存在起很大限制

So life created oxygen and, in turn,

所以说，生命创造氧气，反过来

oxygen has dramatically extended the possibilities for life.

氧气戏剧性的又是生命的必需

And you might think that for us

也许你会认为大气层里

there's no more important gas in the atmosphere.

没有对我们有用的重要气体了

But you 'd be wrong.

那你就错了

There are other gases that are every bit as important

还有其他气体对于我们在地球生存

for our survival on the planet.

有重要作用

These are the greenhouse gases, like carbon dioxide,

有温室气体，比如二氧化碳

that, as we've seen, are pumped out from volcanoes.

如我们所见，从火山中喷发

Without these gases, the average temperature of the planet

没有这些气体，地球的平均温度

would fall to nearly 27 degrees below freezing.

会降到零下27度

But now we're releasing extra carbon dioxide into the atmosphere

但是我们现在排放了过量的二氧化碳到大气中

by burning carbon-based fossil fuels like coal and oil and gas.

因为燃烧碳基矿物燃料，比如煤矿，石油，天然气