> For example, it's quite difficult to imagine how wings evolved, since 1% of a wing seems to offer no fitness advantage Not to nitpick, and I agree with your

> For example, it's quite difficult to imagine how wings evolved, since 1% of a wing seems to offer no fitness advantage Not to nitpick, and I agree with your overall point, but couldn't 1% of a wing be useful for any tree-climbing animal that falls/jumps occasionally? It would allow them to fall/jump a little further without injury by acting as a little bit of a parachute or glider.