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Lesson 26 |
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The past life of the earth |
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What is the main condition for the preservation of the remains of any living creature? |
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It is animals and plants which lived in or near water whose remains are most likely to be preserved, |
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for one of the necessary conditions of preservation is quick burial, |
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and it is only in the seas and rivers, and sometimes lakes, |
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where mud and silt have been continuously deposited, |
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that bodies and the like can be rapidly covered over and preserved. |
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But even in the most favourable circumstances |
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only a small fraction of the creatures that die are preserved in this way |
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before decay sets in or, even more likely, before scavengers eat them. |
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After all, all living creatures live by feeding on something else, |
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whether it be plant or animal, dead or alive, |
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and it is only by chance that such a fate is avoided. |
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The remains of plants and animals that lived on land are much more rarely preserved, |
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for there is seldom anything to cover them over. |
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When you think of the innumerable birds that one sees flying about, |
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not to mention the equally numerous small animals like field mice and voles |
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which you do not see, |
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it is very rarely that one comes across a dead body, except, of course, on the roads. |
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They decompose and are quickly destroyed by the weather or eaten by some other creature |
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It is almost always due to some very special circumstances that traces of land animals survive, |
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as by falling into inaccessible caves, or into an ice crevasse, |
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like the Siberian mammoths, |
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when the whole animal is sometimes preserved, as in a refrigerator. |
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This is what happened to the famous Beresovka mammoth |
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which was found preserved and in good condition. |
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In his mouth were the remains of fir trees--the last meal that he had before he fell into the crevasse and broke his back. |
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The mammoth has now been restored in the Palaeontological Museum in St.Petersburg. |
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Other animals were trapped in tar pits, |
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like the elephants, sabre-toothed cats, and numerous other creatures that are found at Rancho la Brea, which is now just a suburb of Los Angeles. |
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Apparently what happened was that water collected on these tar pits |
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and the bigger animals like the elephants ventured out on to the apparently firm surface to drink, |
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and were promptly bogged in the tar. |
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And then, when they were dead, the carnivores, |
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like the sabretoothed cats and the giant wolves, |
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came out to feed and suffered exactly the same fate. |
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There are also endless numbers of birds in the tar as well. |