Any life we find will probably be very simple.
The following opinion is based on a sample size of 1 - our Earth. It also includes bits that I learned from reading Rare Earth. This book expands the equations used by Carl Sagan, et. al, in the 1960's that talk about life on other worlds.
The bottom line is, using these equations and being optimistic with the assumptions, I came up with about 2 million worlds in our galaxy that may have complex life. Being very pessimistic, I came up with just under 200. There are approximately 500 billion stars in our galaxy. Poor odds no matter how you look at it.
I think we will find space to be very lonely...
Chaunte
+++
I wish the galaxy was like that in Star Trek or Star Wars - a new civilazation to be found in just about every star system. However, I have serious reservations.
We have found traces and microfossils of primitive life. These bits of evidence go back about 3.7 billion years - right after the Great Bombardment that scared both the Earth and Moon.
We didn't have a free oxygen atmosphere until about a billion years ago. That gives us about 22% of Earth's history with a breathable atmosphere.
Sexual reproduction began about 700 million years ago.
And the Pharazoic, our present Eon which includes fossils with hard-parts (shells & bones) didn't start until 544 million years ago.
That makes our planet pretty devoid of life for about 88.2% of Earth's history, assuming a planetary age of 4.6 billion years.
Let's add technology into the calculation.
Our branch off of the evolutionary tree goes back approximately 1.6 million years. That would be 0.034% of Earth's history. (I know that we can go further back, but this branch is a direct lead to us - Homosapien Sapien.)
Our Western Civilization can be traced back about 8000 years, really starting with the flooding and creation of the Black Sea about 5600 BC. That is about 0.00017% of Earth's geologic history. (In Search of Noah's Flood - by Pitman & Ryan)
Lastly - the technology to hear signals from another world has only been around since the early 1960's. That's approximately 0.6% of Western Civilization's history & 0.000001% of Earth's geologic history.
Given all this, and humanity's propensity for building the bigger & better bomb, is a a technologically advanced civilization doomed from the start? To steal a line from the remake of the movie On The Beach, "It took humanity four and a half billion years to unlock the secrets of the universe. And what do we do with it? We blow ourselves up!"
