It might be just about the mutation rate being "higher" or "lower" but also about the volume of reproduction. Even with higher or lower mutation rates, failed e

It might be just about the mutation rate being "higher" or "lower" but also about the volume of reproduction. Even with higher or lower mutation rates, failed embryos/offspring can be offset by higher levels of reproduction. Think how mice reproduce huge numbers of offspring versus humans and many other mammals supporting only 1 at a time. I would also add that volume of reproduction and lifespan of an organism also plays a role. Even if your mutation rate is "low" but you reproduce a lot and have a short lifespan (think like fruit flies) then you could offset slow mutation because your generational mutations are happening quickly. In short, mutation rate can't be the only factor that might be selected for given environments that might be experiencing huge amounts of change.