It is interesting that scientists are finding so many comparatively minor mutations that extend the healthy life spans of lower animals; why didn't evolution lead to those mutations in the first place? From Ouroboros: "Why, then, are these artificially created mutant alleles not the wildtype? In other words, if lacking a particular gene makes an animal longer-lived and more vigorous, why do all wildtype members of the species have the gene in the first place? ... longer-lived mutants are significantly less fit, in an evolutionary sense, than the wildtype. ... the fitness decrease isn't caused by the overall decrease in lifetime fertility, but rather the delay in early-life reproduction. This makes sense, in the relentless logic of exponential growth: The earlier one reproduces, the earlier one's progeny are available to do reproduction of their own. ... It's pretty clear that eventually the short-lived early-reproducer would out-compete the long-lived late-reproducer, even though [the] total lifetime fertility of the longer-lived variant is actually higher. ... Traits that shorten the overall lifespan can be positively selected for if they increase the reproductive success (fitness) of the organism." Which is a tragedy of biology inflicted upon our ancestors - but we are now in a position to start to do something about it.