FYI, choosing to not have kids doesn't mean you get "Darwin'ed out"... We have moved past "survival of the fittest" as a species. While we are still evolving, it's moved beyond simply the most fit individuals reproduce. In order for that concept to work we would have to have a significant child mortality rate (i.e. <16 years old).
If you're talking about removing ourselves from the evolutionary gene pool, well I don't believe that I *have* to pass on my genes to contribute to society. Beyond that, how many people remember their ancestors prior to their grandparents and potentially great grandparents? So essentially I'm irrelevant after 3-4 generations anyways and will be forgotten. So you get to "live on" in your genes. Who the fuck cares? You're still dead...