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Is Intelligent Life Inevitable?

Consider this...
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stack of pennies spacer.gif
Fifty billion pennies lined up would wrap around Earth 3.9 times.


Nothing demonstrates the improbability of the origin of high intelligence better than the millions of ... lineages that failed to achieve it. How many species have existed since the origin of life? ... 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.
--Ernst Mayr, Bioastronomy News, Third Quarter 1995

In the early days of such debates ... writers argued that an enormous number of individually unlikely steps were required to produce something very like a human being, a "humanoid"; that the chances of such a precise repetition occurring on another planet were nil; and therefore that the chance of extraterrestrial intelligence was nil. But clearly when we're talking about extraterrestrial intelligence, we are not talking -- despite Star Trek -- of humans or humanoids. We are talking about the functional equivalent of humans -- say, any creatures able to build and operate radio telescopes. They may live on the land or in the sea or air. They may have unimaginable chemistries, shapes, sizes, colors, appendages and opinions. We are not requiring that they follow the particular route that led to the evolution of humans. There may be many different evolutionary pathways, each unlikely, but the sum of the number of pathways to intelligence may nevertheless be quite substantial.
--Carl Sagan, Bioastronomy News, Third Quarter 1995

(Boldface added.)

Is intelligent life an inevitable result of evolution?

Yes / No

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