Heads of the dead

R544 Current Biology 26, R543–R576, July be repaired, replaced and renewed, and in principle this renewal could go on indefi nitely. And at least in the freshwater polyp Hydra, there don’t seem to be any signs of senescence. But from an evolutionary perspective, things look different. Typically, many organisms die before they reach old age, due to circumstances beyond their control, like being eaten by someone else. This means that mutations that might weaken or even kill the organism at a late stage of life are no longer weeded out by selection and accumulate in the population. And likewise, there is selection for mutations that increase fi tness early in life, even if they have opposite, negative effects on survival later in life. From an evolutionary point of view, ageing and death appear to be all but inevitable. Semelparous organisms are no exception. But a sudden, probably self-regulated death after reproduction can only evolve if it entails some sort of fi tness benefi t for the dying. And what precisely these benefi ts might be for the female octopus isn’t clear. Eventually, the octopus’ controlled death mechanism, no matter how it works and how it evolved, is yet another example of the reign of death over the lives of animals. This is because the evolution of semelparity itself is thought to be a consequence of age-specifi c patterns of mortality, where adults suffer a comparatively higher risk of death than juveniles, such that it becomes more worthwhile for them to invest as much as possible of their resources into a single ‘big bang’ of reproduction. No matter how you fl ip it, death reigns over life and evolving organisms really exemplify that Heideggerian notion of Being-Toward-Death. And of course, ultimately, a large swathe of the evolutionary adaptations that characterise the diversity of life on earth are nothing but devices to escape death. This dark force of biology is what our special issue tries to cast some light on, in its many guises.