Is the theory of evolution being disproved by bats?
Take a look at this little fellow:



It's a flying squirrel &mdash; a shy little nocturnal rodent which lives in trees and, despite its name, does not actually fly.  It does, however, have a skin membrane called a patagium between its fore and hind limbs which allows it to glide from tree to tree and thus evade ground predators.

It's not hard to see how the flying squirrel's patagium may have evolved: after all, ordinary squirrels, to which the flying squirrel is indeed related, also spend most of their time in trees and avoid the ground, often performing quite impressive leaps to cross from one tree to another.  With sufficient pressure to minimize time spent on the ground, any little morphological changes that allowed longer leaps would be favored by natural selection.

Indeed, there are plenty of other groups of mammals which have independently evolved very similar adaptations to gliding.  Given how many small arboreal mammals there are, this is perhaps not surprising.  What's special about bats is not the fact that they possess flight membranes &mdash; it's that they're the only group of mammals, so far, to have taken the next step to actual powered flight.