EXTRAORDINARY LIFE-SPANS IN ANTS - A TEST OF EVOLUTIONARY-THEORIES OFAGING

Senescence presents not only a medical problem, but also an evolutiona ry paradox because it should be opposed by natural selection. Evolutio nary hypotheses propose that ageing evolves as the necessary cost of p rocesses increasing early reproductive success(1,2), or because of wea ker selection against late-acting mutations(3). A prediction of these hypotheses is that the rate of ageing should increase and the average lifespan decrease as the rate of extrinsic mortality increases(1-7). A lternatively, non-adaptive, purely mechanistic hypotheses invoke damag e to DNA, cells, tissues and organs as being the unique cause of senes cence and ineluctable death of organisms(8). Here we show that the evo lution of eusociality is associated with a 100-fold increase in insect lifespan. Such an increase is predicted by evolutionary theories beca use termite, bee and ant queens live in colonies that are sheltered an d heavily defended against predators. Moreover, a comparison of ants w ith contrasting life histories also reveals an association between lif espan and extrinsic rate of mortality. These results provide strong su pport for evolutionary theories of ageing, as purely mechanistic hypot heses of senescence do not propose any association between the rate of extrinsic mortality and lifespans.