新概念英语4册第26课

The past life of earth

It is animals and plants which lived in or near water whose remains are most likely to be preserved, for one of the necessary conditions of preservation is quick burial, and it is only in the seas and rivers, and sometiomes lakes, where mud and silt have been continusly deposited, that bodies and the like can be rapidly covered over and preserved.

But even in the most favourable circumstances only a small fraction of the creatures that die are preserved in this way before decay sets in or, even more likely, before scavengers eat them. After all, all living creatures live by feeding on something else, whether it be plant or animal, dead or alive, and it is only by chance that such a fate is avoided. The remains of plants and animals that lived on land are much more rarely preserved, for there is seldom anything to cover them over. When you think of the innumerable birds that one sees flying about, not to mention the equally numerous small animals like field mice and voles which you do not see, it is very rarely that one comes across a dead body, except, of course, on the roads. They decompose and are quickly destroyed by the weather or eaten by some other creature.

It is almost alwasy due to some very special circumstances that traces of land animals survivae, as by falling into inaccessible caves, or into an ice crevasse, like the Siberian mammoths, when the whole animal is sometimes preserved, as in a refrigerator. This is what happened to the famous Beresovka mammoth which was found preserved and in good condition. In his mouth were the remain of fir trees -- the last meal that he had before he fell into the crevasses and broke his back. The mammoth has now been restored in the Palaeontological Museum in Leningrad. Other animals were trapped in tar pits, like the elephants, sabre-toothed cats, and numerous other creatures that re found at Rancho la Brea, which is now just a suburb of Los Angeles. Apparently what happened was that water collected on these tar pits, and the bigger animals like the elephants ventured out on to the apparently firm surface to drink, and were promptly bogged in the tar. And then, when they were dead, the carnivores, like the sabre-toothed cats and the giant wolves, came out to feed and suffed exactly the same fate. There are also endless numbers of birds in the tar as well.

在水旁边生活的动植物遗迹比较容易保存。因为保存的一个必要条件就是快速被埋葬。只有在海边，河边或者湖边这些泥土和淤泥持续累计的地方，身体可以被快速的覆盖并保存起来。

但是即便是在最理想的条件下仍然只有一小部分生物在腐烂或被是食腐动物吃掉以前保存下来。毕竟，所有活的动物都需要吃掉其他的东西，无论是植物还是动物，活的还是死的。能逃避这种命运只是偶然的。动植物的遗体在陆地上很少能保存下来，因为没有任何东西覆盖。可以看到无数的飞行鸟类，还不包括同样大量的田鼠，野鼠，很少有尸体，除非是在路上。它们很快因为天气被破坏或者被其他动物吃掉。

在一些很特殊的情况下陆地上的动物痕迹可以保存下来。例如掉入一个无法出来的山东，或者掉入冰缝中。就象西伯利亚的猛犸象，有时整个动物就象在冰箱总一样，被保存起来。就象著名的Beresovka猛犸象，保存的很好。而它的嘴里还有杉木的痕迹，那是它掉入裂缝摔断背部前的最后一顿饭。这头猛犸现在被保存在Leningrad的Palaeontological博物馆。在洛杉矶市郊的Rancho la Brea, 一些动物如打响，长齿猫，以及其它大量动物被困在柏油坑中。显然，正中情况是因为柏油坑中的雨水，大型动物，如象，冒险在表面饮水，结果迅速陷入了沼泽。随后，当它们死亡时，长齿猫和狼等食肉动物在这里觅食，结果遭到了完全相同的命运。这里也有不计其数的鸟类。