Is Evolution Reversible

It is theoretically possible, but highly unlikely that due to changing conditions, a species would revert to an ancestor species. More likely would be a new set of mutations that may end up with a similar looking species, or a species that has similar capabilities, but if you were to do an actual genetic sequence, it wouldn't match the progenitor that it now resembles again.

Who said it's the same solution? Just because they look similar doesn't mean they are duplicates. Evolution, and natural selection in particular, are still constrained by the laws of physics. If selection is moving towards a flying model, the ultimate "design" is going to necessarily resemble the original flying model despite having, perhaps, an entirely different set of genes creating the apparatus.

It depends on the environment and the population size. If you have a small number of individuals, then yes, the chance of it evolving is lower than if there are a large number of individuals. Assuming the environment is such that flying is better than not flying, from a reproductive success standpoint, and the basic bodyplan of the individual already comes with the necessary precursor apparatus, then any mutation would have to build on what is already there, and so will probably end up with something similar.It is entirely possible, depending on the number of changes since the original flying type, for an exactly opposite mutation to occur, resulting in a wing that is genetically identical to the original, but it is more likely that a merely similar one would arise.Edited by Perdition, : No reason given.