[Rexxx]

Originally posted by Slick:
There is a famous equation called the Drake Equation which mathematically sets the probability of life in the universe. You can look it up for further reading. It basically comes out to a mathematical certainty because of the sheer number of stars that we can see that there is life out there somewhere. The real question is what is it like.

Several months ago I read "Rare Earth" by Peter Ward and Donald Brownlee (a paleontologist and an astronomer IIRC).
The rare earth theory is that though bacterial life may be common in the universe, intelligent life - in the form of terrestrial animals and plants - is unique.
Their modifications to the Drake Equation are quite interesting. I do not know enough about the the topics they raised tp prove them right or wrong. Anyway, it's a book well written and full of ideas new to me. I never would have thought of plate tectonics as crucial for evolution on Earth.