Biology works itself out
In any case, by "biology" you're referring to the biosphere? If so, the (potential) risk is that "biology work[ing] itself out" may involve working humans out of the picture as well.
In addition, there's the question of whether the variability in human DNA affects the originally described "nasty self-centered" behavior; if it doesn't, no amount of "natural" variability will achieve the described desired outcome.