" Birds were made by transformation: growing feathers instead of hair, they came from harmless but light-witted men, who studied the heavens but imagined in their simplicity that the surest evidence in these matters comes through the eye. Land animals came from men who had no use for philosophy and paid no heed to the heavens because they had lost the use of the circuits in the head and followed the guidance of those parts of the soul that are in the breast. By reason of these practices they let their forelimbs and heads be drawn down to the earth by natural affinity and there supported, and their heads were lengthened out and took any sort of shape into which their circles were crushed together through inactivity. On this account their kind was born with four feet or many, heaven giving to the more witless the greater number of points to support, that they might be all the more drawn earthward. The most senseless, whose whole bodies were stretched at length upon the earth, since they had no further need of feet, the gods made footless, crawling over the ground. The fourth sort, that live in water, came from the most foolish and stupid of all. The gods who remolded their form thought these unworthy any more to breathe the pure air, because their souls were polluted with every sort of transgression; and, in place of breathing the fine and clean air, they thrust them down to inhale the muddy water of the depths. Hence, came fishes and shellfish and all that lives in the water: in penalty for the last extreme of folly they are assigned the last and lowest habitation. These are the principles on which, now, as then all creatures change one into another, shifting their place with the loss or gain of understanding or folly. "

― Plato , Timaeus