Rather than saying that all the similar adaptations necessary for powered flight evolved separately in the two groups of bats, the alternative explanation is that it is actually the similar neural pathways, associated with visual acuity, that arose independently in flying foxes, flying lemurs, and primates, as all rely on their vision to find food. The microbats, in contrast, rely mostly on their hearing in echo-locating, and never developed these pathways. In trying to understand the origins of bats, researchers can study living animals, but nobody was around millions of years ago to observe the formation of bats, so they have to rely on fossils to supply the evidence of what they propose. What the evolutionist will not show you is any kind of transition between paws used for standing and running, and hand-wings used for flying. He won't show you because there is no fossil of such a creature, and he can't imagine what one would look like.
Birds perch very well right-side up.
Try swallowing while hanging upside-down. Yet bats eat, sleep, and mate upside down, and many also give birth in that position. They will point to examples like Darwin's famous finches, or bacteria that become immune to antibiotics used against them. In 1859 Charles Darwin published his Origin of Species, in which he presented his concept of the evolutionary development of species, based in part on his observations on the Galapagos Islands. Unfortunately, another famous set of observations was not published until 1866, seven years later.