One of the biggest assumptions made in these debates (and integral to the Drake equation) is that the evolution of life is a linear process and naturally proceeds from simple to complex.
This is not borne out by observation.
The evolution of life on our own planet indicates that single-celled life is very likely to evolve on any planet with the right conditions (which in themselves are rare enough). However, the sequence of catastrophic events that happened in just the right sequence to produce the bursts to multi-cellular life and then further jump-start evolution towards a human intelligence are so extraordinary, and so mathematically unlikely to fall in the same sequence anywhere else, that there is a very strong argument that we are the only intelligent life in the universe (which is not remotely infinite).
Think of that responsibility. It's us and ooze.
Bookmarks