The shortage wouldn't be so bad if the bones were distributed evenly through time and space, but of course they are not. They appear randomly, often in the most tantalizing fashion. Homo erectus walked the Earth for well over a million years and inhabited territory from the Atlantic edge of Europe to the Pacific side of China, yet if you brought back to life every Homo erectus individual whose existence we can vouch for, they wouldn't fill a school bus. Homo habilis consists of even less: just two partial skeletons and a number of isolated limb bones. Something as short-lived as our own civilization would almost certainly not be known from the fossil record at all.
如果这些人类化石能够按时间和空间分布得比较均匀的话,即使缺乏,事情也不至于如此糟糕。实际情况当然并非如此。它们东一块西一块地出现,往往令人备尝可望而不可即之苦。直立人在地球存在了100万年以上的时间,他们居住的范围从欧洲的大西洋沿岸一直到中国的太平洋沿岸,然而如果你将所发现的每一个直立人复活,他们还装不满一辆校车。能人的化石就更加少得可怜:只有两副不完整的骨骼和几根孤零零的肢骨。有一些存在时间和我们自己的文明一样短暂的事物,仅仅根据化石记录,几乎肯定是无从考证的。
"In Europe," Tattersall offers by way of illustration, "you've got hominid skulls in Georgia dated to about 1.7 million years ago, but then you have a gap of almost a million years before the next remains turn up in Spain, right on the other side of the continent, and then you've got another 300,000-year gap before you get a Homo heidelbergensis in Germany—and none of them looks terribly much like any of the others." He smiled. "It's from these kinds of fragmentary pieces that you're trying to work out the histories of entire species. It's quite a tall order. We really have very little idea of the relationships between many ancient species— which led to us and which were evolutionary dead ends. Some probably don't deserve to be regarded as separate species at all."