I've always been curios about aging and sex. These two attributes seem to make no sense from an evolutionary perspective, at least in terms of raw numbers. I recently saw a science show that tracked some fish that could reproduce asexually and sexually, and that study pretty much showed that sex is a highly valuable attribute for the red queen scenario we see between pathogens and hosts (ie it kept the hosts alive by having greater genetic diversity and varying disease resistance, whereas the asexually reproducing fish all perished to disease). This makes complete sense to me, in fact we see this very effect in the psudosexual gene swapping in bacteria, also it's noteworthy that our own species has a built in mechanism that increases attraction between individuals with different antigen/antibody detectors/producers. This got me thinking about senescence, and it seems to me the two may be linked. Let's assume you have an organism that doesn't age, it lives for a long time, producing many offspring; when a pathogen comes along and that attacks that organism - many of it's offspring will be affected, which could have a profound effect on an entire population and even species. Now with senescence the parent organism dies, thus forcing more gene swapping and reproduction with other individual organisms, thus increasing the genetic differentiation in the population and presumably the overall disease resistance of the population. In other words I think aging is the price we pay for sex, at least that's how evolution on earth seems to have been driven, since all sexually reproducing organisms I know of age. Does this hypothesis make any sense to anyone else? How would one go about testing this hypothesis? There is some supporting evidence, such as animals with rapid senescence generally have very robust immune systems, such as opossums. I'm interested in others ideas not just my own, which is why I am posting this here.