I just read an article where it was postulated that one third of Sun-like stars host warm, water-bearing planets. Using the Milky Way as the obvious example, a minimum estimate of 200 billion stars of which 7.6% are G-classified (our Sun is a G) yields 15 billion stars with potentially Earth-like planets. At 13 billion years old, I find it inconceivable that there isn't intelligent life elsewhere in the galaxy.

Jump to Fox's new Terra Nova TV show, and more relevently the discussion on the TV/Movies board. Living on a planet without fossil fuels means that the only way to extract energy is to burn things, turn a water/wind mill, etc. until you're able to refine fissionable or create solar panels.

Taken together, I have to wonder if one reason we haven't seen other intelligent life already is because the energy available to make the transition from low-tech energy sources to anything more capable is precluded by the necessity for fossil fuels to serve as an intermediary energy source.

Think about it: how likely is heavy industry - metallurgy in particular - and the following technological society to even be possible if the best you can do is lighting a wood fire?