It's not necessarily that intelligence takes a long time to develop relative to the lifespan of the biosphere, it's that life keeps being reset by these extinction events every few hundred million years. You need not just life, but accumulated complexity to survive. Given a few more million years, the dinosaurs might have made it.

Yep!

Yes, the Kroffts were way ahead of their time. Which makes me wonder what kind of evolutionary dead-end this guy was supposed to represent.

Snort!

The stability of the star system is a very big deal in the arrival of intelligent life. As you suggested, complexity is the key and complexity requires stress... within tight limits.

As the earth shattering asteroids diminished (the gas giants get a lot of credit) it allowed more and more time between the major extinction events. Enough time (this last time) for intelligent life to arise.

But the taming of the solar system took a lot of time.

Were we to go extinct, there might not be time for another shot at intelligent life in this solar system before the sun becomes too unstable.

Another thing to consider is that intelligent self-reproducing life is extremely dangerous. As I see it, a galactic civilization would have several long term solutions. Either destroy it, modify it so it's no longer dangerous, or allow it to evolve "naturally" to become a contributing member of your civilization. The last might require a long hands-off period and is certainly the riskiest of the bunch. Much like the "prime directive" of Star Trek.

But!!

The "Drake Formula" starts with a sample of one, and says- "nah- we're alone."

that seems big somehow.

And HR Puffnstuff?

FIts how??

This thread is ancient.. but I've been listening to older episodes and the subject has come up a lot. Stephen brings up up the paradox a lot but only mentions one or two other options. I can think of MANY reasons we don't see "them" right now.

I can think of a lot of things wrong with Fermi's paradox about why we dont see the universe teeming with life.

- It assumes that life is not extremely rare in the Universe - perhaps only 3 advanced species exists in the entire universe.
- It assumes Et's would want to interact with us. Perhaps they fear contact or deem us not worthy of interaction.
- It assumes Et's would want to explore the galaxy or travel from their home system. Just because Humans want to do it now that has no bearing on the motives of alien minds.
- It assumes that if Et's did want to explore the galaxy they are doing it now, not millions of years ago. Perhaps they did visit Earth in the distant past but found nothing of interest.
- It assumes Et's would be exploring the Universe with technology/methods that we can comprehend/detect. Who says Et's are operating in the geometry of space time we are restricted to? Or that they are emitting radio waves. Or those radio wave sources are not billions of light years away.
- It assumes that Et's would not make every effort to avoid detection if they did have technology similar to our own but advanced far enough to allow interstellar travel
- It assumes that Et's would increase in population over time (this geometrically increasing the number of explored planets) - perhaps there are advanced beings but they exist in small numbers and have not been in our neck of the galaxy for quite some time.
- Perhaps we are in an ET zoo where only limited contact with the specimens is allowed
- Perhaps Et's have been here with us all along but are disguised or hidden.
- Perhaps life is not common in this area of the galaxy or universe
- Perhaps our "owners/wardens/keepers" ward off any potential visitors from third party ET's

These things can combined or stacked:

For example, what if 2 million years ago Et's came to Earth and surveyed this planet and left and have now stopped exploring space all togther and their home system is 20,000 light years away and their planets emits no radio waves. We will never ever know of their existence.