Intelligent life оn отher planets

2) The question of whether alien planets have intelligent beings on them is astill more tangled one. It is so means certain, that intelligence of human quality is the normal culmination of evolution. Some conditions may be favorable to life but not to high intelligence. The earth’s oceans, for instance, have no appreciably intelligent creatures, except for mammals such as dolphins and seals. To judge by this analogy, which is risky, an alien planet that is completely covered by water will probably have no animals more intelligent than the earth’s fish. The human combination of a large brain and a tool-holding hand is even more fortuitous. It would be expected that a long series of special circumstances was necessary to develop it. If any of them had been lacking, the earth would have continued for billions of years more, perhaps for the life of the solar system, without achieving really high intelligence.

3) On the other hand, intelligence undoubtedly has important survival value. Evolution on the earth has generally moved in the direction of more highly developed brains. Fish have better brains than the marine worms from which they evolved, and amphibians, reptiles and mammals have successively better ones. If man had not developed his large brain, some other mammal, perhaps, the racoon, might have done so in a few tens of millions of years. Evolutionists suggest that intelligence should be in the cards for any planet where conditions are reasonably favourable for it.

4) But does intelligence imply that civilization exists? Here is another question hedged with unknowns. In the case of the earth, more than 200,000 years must have passed between the appearance of the first men with really large brains and the first human society that could be called civilized. But with only one example to judge by, this incubation period cannot be called standard for all inhabited planets. It may be unusually short or long. In any case, there should be plenty of time. The earth produced creatures capable of technical civilization in about five billion years, less than half of the 13 billion years that the sun would be expected to shine steadily. Since smaller stars of the sun’s type are extremely numerous and shine even longer, their planetary systems might have an even better chance – so far as time is concerned – to develop civilization.

5) Even when civilization has begun, a high technical civilization is by no means certain. The first civilized human communities we­re agricultural villages in the Middle East about 10,000 years ago. Since that time, human civilization has experienced many ups and downs. For many long periods, it must have seemed that civilization was a self-limiting process that could never rise above the handicraft level.

Exercise 2. Read paragraph 1. State the topic of the paragraph. Identify three periods, in the history of the problem. Characterize the ideas prevalent in each period. Find the sentences which provide arguments for or against the possibility of life on other planets.

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