3 ms·

> if you happen to have a life strategy which makes you momentarily better off, but permanently worse off, you may die of unrelated causes before suffering a ne

• AnthonyMouse 14y ago
  >I would guess that the bats get around this by getting so much extra EV from occupying the unique ecological niche of "flying mammal" that the ability to occupy that niche overwhelms the negative aspects of a smaller mutation rate. You're assuming a smaller mutation rate. The article points out that bats generally don't live to die of old age, something else usually gets them first. A longer theoretical lifespan doesn't reduce the mutation rate if lifespans in practice are still modest. (If the first couple of hits on Google are any indication, bats typically live for a couple of decades.)
  • csense 14y ago
    > if lifespans in practice are still modest They aren't. The article says: "For an animal of their size, [bats] also age very slowly..." I'm assuming that, without their gene repair mechanism, they would have been more in line with other animals their size, and occasionally died of old age. So the gene repair mechanism does extend the bats' lifespan. To do good science, of course, you'd have to confirm this by an experiment to raise some bats that lack the gene repair mechanism and measure their deaths due to old age against a control group. Or better yet, do a fantastically expensive long-term experiment comparing bat colonies with and without the DNA repair mechanism, and measure their genetic drift over time. Of course, I haven't done those experiments. If someone else does them, and shows results contradictory to my assumption, it'll be a great scientific discovery. But in the absence of evidence to the contrary, it seems like it's a safe bet that the DNA repair mechansim would reduce mutation rates on its own, and anything that makes the bats live longer would also reduce mutation rates on its own, and having both longevity and DNA repair together would reduce mutation rates at least as much as either by itself. You may say decades of lifespan is "modest" by human standards, but much more relevant comparisons would be to bats without the DNA repair mechanism -- or, if data is lacking on those, to closely related mammals of similar size.
• thaumasiotes 14y ago
  > My understanding of why we didn't evolve to have better gene repair and longer lives is that the ideal death and mutation rates in terms of species survival is some finite number greater than zero. Near-immortality, eternal youth and perfect genome repair would be great from an individual perspective, but from a species perspective, those things reduce the ability for genetic innovation. If this is the dominant effect in how organisms deal with aging, it can explain why we observe aging all around us in the world, but it predicts that, if you track a population over time, you will see lifespans creeping steadily upward. I don't believe this is actually observed. The phenomenon you describe is generally invoked to explain sexual reproduction. But it is not unheard of for a particular ecological niche to be dominated by a clonal organism; it's just that those clonal organisms sometimes (inevitably?) "fail" very suddenly in the face of new competition. So both ends of the tension between individual good / species-level good can be observed in the world, and it seems that in the case of sexual reproduction species-level good mostly dominates. I'm not aware (disclaimer: I am an uninformed layperson) of similar conflicts between immortal species and aging ones for an ecological niche. The picture I have of the world is that certain niches are filled by immortal organisms, and other, more macroscopic niches are filled by mortal ones. Though typing this out makes me wonder about things like jellyfish. To sum up, without seeing much evidence of strong selection for increasing lifespans, or increasing reproductive spans (the individual perspective counts!), and with the general bias not to invoke group selection where individual selection will do, the mortgaging-the-future approach to aging seems like a better explanation to me.