The Great Filter

Nick Bostrom makes one of the most interesting arguments about life on other planets that I've ever read.

After 50 years of looking, we haven't found any signs of advanced civilization on other planets. If it was out there, it would be very easy to find because intelligent life advances so quickly (a million years is a blink in astronomical time). If we survive for another million years, we'll colonize the entire galaxy. If some other intelligent creatures exist, there are good reasons why they wouldn't/couldn't hide from us, "Prime Directive" be damned. Therefore, no one is out there.

Since there are so many Earthlike planets but no advanced life, there must be some great filter keeping it from happening. That filter could be something we've already crossed (and we're the extremely lucky ones) or else the filter is ahead of us, in which case we're doomed.

If there is life on Mars, we're probably doomed and the filter is ahead of us. The more advanced that life is/was, the more doomed we are.

However...

I think it's likely that we're the only ones. Our Earth is very odd in having a wildly oscillating climate that goes into ice ages every 10,000 years or so. Humans emerged just as the climate started to oscillate. It opened up a niche for a general purpose creature like ourselves that's "software based" and very adaptable. Our intelligence is a big hinderance to our survival since our brains cost a lot in terms of nourishment. So we only exist because there's a big niche for software based creatures that can fly, run fast, and be ferocious only by developing extremely complex tools. It's much easier to fly by having the right hardware, like birds. It's easier to be ferocious by being more like a lion than to develop sophisticated weapons.

I think we're an oddity in our galaxy and we will end up colonizing the Milky Way and possibly beyond. It's not very difficult to do it given what we already have and given a million years or so of time. If Americans don't do it, the Chinese will, or the Indians, or some future civilization ten thousand or a hundred thousand years in the future.

There's talk of reaching an actuarial escape velocity where anyone who survives beyond a certain time period is likely to live for an extremely long time: a thousand years or more. Our level of medicine is only now becoming advanced, with drugs that we control at the molecular level rather than simply being medical hunter-gatherers. I believe the future is going to be very strange.