Guns, Germs and Steel is a very thought-provoking book. One of it's theorems is that certain cultures - largely due to geographical reasons - were incapable of getting past certain technological and cultural development points. For example, one of his references is New Guinea, which has had some sort of civilization at roughly the same level for thousands and thousands of years. And the book's argument is that it wasn't that the people were stupid or incapable - but that they were missing crucial factors like animals to domesticate, efficient crops, and the right kind of land, and that stalled development.
So my question is this - could Earth be a sort of galactic New Guinea? Is it possible that due to factors of the planet - primarily limited resources and our gravity well - that humanity is stuck here, that we'll plateau and not be able to get past that point? Or that our current technology is leading to irreversible changes that will prevent us from continuing to develop, through climate change or hitting peak oil?
I can see how this would be a tricky question to answer, but here's a couple of potential ways I can see:
Analyze the resource costs of space exploration using current technology. What we'd need to do to find another viable planet and colonize it. Obviously if that's within the realm of possibility we're ok (or at least if we self-destruct it's our own fault). A self-sufficient colony in our solar system would be ok, interstellar would be better.
Realistic technologies within our current understanding of physics that would break us out of our current dependence on limited oil reserves, as that should make it at least theoretically possible to colonize the solar system and possibly go interstellar. And would also help prevent self-inflicted doomsday scenarios.
Some other answer that usefully addresses the question - i don't want to limit possibilities, hopefully there are other ways to address this that I haven't thought of.