@f740824b @e0c06ded Vertebrate animals have ageing. It's less obvious that invertebrates, eukaryotes, and non-animals (eg. plants and fungi and archaea) have baked-in senescence: indeed, many don't. (I speculate wildly that senescence is a side-effect of cellular differentiation into specialized tissues including the immune system, and didn't get selected out because it didn't impair reproductive fitness. Cf. naked mole rats—mammals with extreme longevity and cancer-resistance.) 

 @0c1a9324 @e0c06ded It may be a side effect but it seems very pragmatic and that argues for evolutionary selection. It has value for a species. But I think DNA has some secret we haven't uncovered yet.