But stepping out onto theopen savanna also clearly left the early hominids much more exposed. An uprighthominid could see better, but could also be seen better. Even now as a species,we are almost preposterously vulnerable in the wild. Nearly every large animalyou can care to name is stronger, faster, and toothier than us. Faced withattack, modern humans have only two advantages. We have a good brain, withwhich we can devise strategies, and we have hands with which we can fling orbrandish hurtful objects. We are the only creature that can harm at a distance.We can thus afford to be physically vulnerable.

但是，走向开阔的草原，早期人科动物显然更暴露自己。直立行走的人科动物看得更清楚，但也被看得更清楚。即使是现在，作为一个物种，我们在野外会几乎荒唐地感到不安全。我们叫得出名字的大型动物差不多都比我们的身体要强壮，动作要快，牙齿要锋利。面对攻击，现代人类只有两种优势。我们有发育良好的大脑，可以想出对付的办法；我们有灵巧的双手，可以投掷或挥舞具有杀伤力的东西。我们是惟一能在一定距离内杀伤敌人的动物，因而也是不怕受到攻击的动物。

All the elements wouldappear to have been in place for the rapid evolution of a potent brain, and yetthat seems not to have happened. For over three million years, Lucy and herfellow australopithecines scarcely changed at all. Their brain didn't grow andthere is no sign that they used even the simplest tools. What is stranger stillis that we now know that for about a million years they lived alongside otherearly hominids who did use tools, yet the australopithecines never tookadvantage of this useful technology that was all around them.

一切因素似乎都有利于大脑的迅速进化，但那种情况似乎并没有发生。在300多万年的时间里，露西和她的南方古猿同伴们儿乎没有发生任何变化。他们的脑容量并没有增大，也没有任何迹象表明他们使用过一种哪怕最为简单的工具。更为奇怪的是，我们现在知道，与他们一起生存了将近100万年的其他早期人科动物曾经使用过工具，而南方古猿却从未利用他们周围的这些有用的技术。