Extracts from "Can SETI Succeed? Not Likely" by Ernst Mayr
Below is something I copied from the a page at the Planetary Society. I find the essential arguements compelling. I must be explained in the context of my belief that E.T does exist.
The Planetary Society: SETI Page "The elaboration of the brain of the hominids began less than 3 million years ago, and that of the cortex of Homo sapiens occurred only about 300,000 years ago. Nothing demonstrates the improbability of the origin of high intelligence better than the millions of phyletic lineages that failed to achieve it.
How many species have existed since the origin of life? This figure is as much a matter of speculation as the number of planets in our galaxy. But if there are 30 million living species, and if the average life expectancy of a species is about 100,000 years, then one can postulate that there have been billions, perhaps as many as 50 billion species since the origin of life. Only one of these achieved the kind of intelligence needed to establish a civilization.
If Mayr is correct, then why is intelligence so unique or to put it differently, why is so difficult to achieve? Mayr does not answer this question adequatly. He does however give two possibilities;
" One is that high intelligence is not at all favored by natural selection, contrary to what we would expect. In fact, all the other kinds of living organisms, millions of species, get along fine without high intelligence...."
"The other possible reason for the rarity of intelligence is that it is extraordinarily difficult to acquire. "
Both these possibilities require further elaboration. For what Mr. Mayer is actually saying is that all forms of adaptation are equivalent. This implies that natural selection is ammoral. I would agree with that conclusion however I would not go as far as to believe that all forms of adaptations are equivalent. Furthermore the equivalence principle implies that evolution is not directed. However, evolutionary history has demonstrated that life has evolved from simpler to more complex organizations. This clearly demonstrates that adaptations are not equivalent in time. As for the second possibily, its essentially a concequence of Mayr's first arguement so doesn't actually explain anything.
I believe that intelligence is inevitable in a complex ecosystem. To the extent I am willing to postulate the following principle.
Only a single species will be endowed with high intelligence on any planet supporting a complex ecosystem.
Though I can only conjecture at this point, I do believe that it is not a species that becomes intelligent but an ecosystem that "seeks" intelligence like a chaotic system seeking a basin of attraction. Intelligence can I feel only be explained in the context of viewing the whole ecosystem as a dynamic system. Research along those directions will I believe lead the the vidication of my postulate.