And this leads us to the main point of the Blind Cave Fish’s Tale. It is a tale of Dollo’s Law, which states that evolution is not reversed. Is Dollo’s Law disproved by the cave fish’s apparent reversal of an evolutionary trend, shrinking again the eyes that grew, so painstakingly, over past evolutionary time? Is there, in any case, some general theoretical reason to expect evolution to be irreversible? The answer to both questions is no. But Dollo’s Law has to be correctly understood, and that is the purpose of this tale.
