I have to admit the numbers in whatever version of the Drake equation and then the Fermi paradox are hard to dismiss. Even at non-relativistic speeds, aliens should have had plenty of time to colonize the galaxy or even the universe. But I guess that's why it's called a paradox -- why don't we have undeniable evidence of their presence?

Far more plausible than the biblical stories. Actually the "life brought by a comet" theory and similar celestial-microbe ideas are even more compelling.

I believe in the ancient astronaut theory probably about as much as I believe in the Christian god.