Dale closed his eyes, trying to mentally imagine what sort of strange evolution might make such a thing even possible.  It was something he sometimes struggled with, even thinking about human evolution.  How could an eye come about?  What use was a half-eye?  How did some of the ponies get wings, some of them get horns, and some of them get neither?  And the dusky guard who had been with Princess Luna—he had cat-like eyes and leathery bat-wings, but otherwise looked much like the pegasus guards.  How could that have happened?  Or was he now trying to put too much faith on one outlier?