>>49954653Because the ones that had black spots in those area got eaten slightly less often than the ones that didn't, as they were sometimes mistaken for a snake. Many times over many generations and the black spot havers live long enough to have more babies, thus more and more of the population has the spots. Then when nearly all of them have the spots, the ones which look closest to actual eyes are the ones getting mistaken for snakes more often. So on and so forth until you end up with more and more realistic eyes. This is actually one of the easiest forms of evolution to understand. Sensor organs in general are much more baffling.
