"There might be billions of worlds full of dinosaur analogs running around happily eating and growling till their star burns out...and that might be all that you can expect out of life in the general case when it happens."
This is the essence of the Fermi paradox I believe. (And I've ordered a copy of the book mentioned below, it looks intriguing) So what hypothesis could support billions of iterations of 'life' evolving into the multicellular form we see today and in our past, and so few evolving technology?
I totally agree it is a somewhat useless question to ponder but I can't help it.
Probably just a function of environmental input and enough generations optimizing along directions that matter more for species propagation than a large, energy burning cognitive organ. Keep in mind, it appears that Human level intelligence seems to have (so far) only evolved maybe a handful of time maximum in planetary history...and AFAWK only along a fairly specific mammalian family line that happened to live on part of the planet with fairly specific thermal/environmental and energy availability properties.
On a planet slightly warmer than the Earth, the dominant species might be selected to have heat management organs we're not even aware of; or a planet with more landmass vs. ocean, the ability to handle dry climates; or a planet with two moons and higher gravity an efficient metabolism and ambulatory system...some kind of reptilian slug perhaps?
Are savannas necessary to culture space faringness? Or could a planet with no moons, shotgunned with equally dispersed Guam sized islands provide the necessary conditions?
It's useless, but an incredibly fun thought experiment.
Philosophically, even an Ark ship, with technology capable of sustaining a population of humans for a million years wouldn't fit the bill since I'd argue that by the time the descendants arrive they:
a) would probably not be the same species anymore, having evolved over thousands of generations for ship life
b) wouldn't be the same civilization anymore, having developed their own micro-civilization in the intervening years -- they'd no longer be representatives from their home civilization...any more than I as an American can be a representative for the European civilizations I am descended from when I travel to Asia
c) their home population and civilization will have evolved and diverged from the Ark's population and civilization regardless of the Ark's conditions. Even if the population on the Ark was put into some kind of suspended animation for the length of the trip (preserving the both the original species and civilization) they'd be representing a species and civilization that no longer existed
There might be billions of worlds full of dinosaur analogs running around happily eating and growling till their star burns out...and that might be all that you can expect out of life in the general case when it happens.
"Why didn't the Dinosaurs develop space flight?" Why don't we? Again, in absolute terms of the characteristics we're requiring of an alien civilization, we're not really any closer (in measurable absolute terms) to visiting Vega than a struggling ape is. The furthest distance a human has ever traveled off of the Earth is very slight navigational/rounding error when going to another Star.