The local variation in a population is reversible (micro-evolution) but is macro-evolution reversible? Obviously not exactly but if conditions changed then would evolution back-track?
Evolution doesn't have a direction so surely it is possible for it to go backwards?
You just joined and proposed three topics. I'll promote one (Is Evolution Reversible) and close the other two (Human Evolution and Evolution of the Eye). If things go well with the promoted topic then feel free to repropose the ones I closed sometime down the road.