时差N小时 我们为什么要睡觉?(下)（在线收听）

At night, humans do rather poorly: we can't see objects well, our color vision is entirely lost,

晚上，人类的活动力相对差些。我们看不太清物体，我们的颜色辨别也完全消失了，

and we don't have the smelling or hearing acuity of other animals.

而且我们还没有其他动物那么敏锐的嗅觉和听觉。

So it actually does make sense to have us stay put during the dangerous period when "nocturnal," or night-waking, animals are on the prowl.

所以在那些夜间活动的动物们出没觅食的危险时刻，我们保持原地不动，确实是很有道理的。

And one sure way to make sure we don't stumble around and get lost or eaten is to have us immobilized for seven or eight hours,

一个确保我们不会跌跌撞撞，不会迷路或者被吃掉的稳妥方式就是，每天休息七到八个小时，

rising again only when the light is back and our survival chances are better.

天亮了我们再起床活动，这样我们的生存机会会更好地得到保障。

It's not the only reason we sleep; but in terms of evolution, it may have been one of the first reasons --

这还不是我们睡觉的唯一原因;但就人类进化而言，它可能是其中一个首要原因——

perhaps even the most important one.

甚至还可能是最重要的一个原因。