What you say it's true, although harsh and in some sense mean. But in my opinion, in some cases science has accelerated what nature would have done by itself. Consider vaccination and smallpox for example: if it's true that nature dictates survival of the fittest, and someone having smallpox is far from being the fittest, it means that in the long run the disease would have disappeared anyway. And I think that science, medicine in this particular case, is pushed by altruism in the first place, and here we come back to the never ending dilemma: do you save lives because you care about the others, or you do it because you feel better with yourself? Is altruism just another form of egoism?