Brian Robinson commented in "Discussion" (9/20/98) about whether or not humans are immune from extinction and why: the key element as I see it is that we are the first species (as far as we know) that can (now or in the near future) make deliberate changes in our own genome if we so choose. No other species, not the brightest Bonobo nor dolphin, can extract or insert new genes into our cells. No other species can extract genes from one species and then introduce them into cells of another species. Whatever trait(s) may push us towards extinction could be altered by altering our genetic make-up. Thus, in theory, we COULD "engineer" changes in the human genome that might keep us "fit" in almost any possible environmental scenario. Whether the current version of Homo Sapiens has the "psychological" capacity to undertake such an endeavor is the big question. Given our (evolved) propensity for superstitious fears about "tampering with Godís work," it is doubtful that humanity could ever agree to make such changes as are needed.
BTW, this reminds me of a science fiction story about humans colonizing other planets in the far future. The point of interest was that, rather than "terraform" a hostile planet to be compatible with humans, they "genoformed" some of the humans so that they were compatible with the planet. Does this sound evil or enlightened?