> 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,

> 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.