Natural selection and "survival of the fittest" (the latter a term Darwin despised) are much-bandied around by people who often haven't a clue what they're talking about, but who think they do. Natural selection is all about the non-random survival of genes within a gene pool. It has nothing to do with "weeding out" the weakest or slowest wildebeest, etc. That is to consider selection on entirely the wrong hierarchical level, something Darwin counselled against. Similarly with "survival of the fittest". That concept, misrepresented, led to Hitlerism, and Darwin would be turning in his grave. It's a term I try to not use, as selection is all about differential survival within a species, not between species or between "races" (which, in human terms, don't exist).