Shrews are little mousy creatures, some of which hunt for insects in trees. An official candidate for the evolutionary ancestor of the bat is the shrew. So is there some fossil evidence for this remarkable evolutionary development?
No, not a single bone. In fact, what is said to be the most ancient bat fossil is essentially identical in all important features with a modern bat. There is not a trace of fossil evidence for any intermediate forms.
Thus, for the history of the supposed evolution of bats we are forced to use our imagination: there was this little shrew that yearned to catch the insects that got away because they could fly. Some shrews were born with slightly longer finger bones in their front feet. For some unknown reason these longer fingers were preserved by natural selection. They had some unknown advantage. Generation by generation, by chance mutation and natural selection, the finger bones became longer, and flaps of skin appeared between them. After many generations the shrew had become a bat and flew away. Isn’t it great what evolution can do?
But let’s think about the little animal half-way evolved to his graduation flight. Shall we call him a ‘shrat’ or a ‘brew’? His finger bones are hanging down to his ankles, so he can no longer run on all fours. Thus he must walk on his two hind feet. But they are well along to becoming bat’s feet, adapted not to running and climbing, but to hanging upside-down in caves and belfries. There are loose flaps of thin skin between his fingers, but his ‘wings’ are not yet evolved far enough to permit him to fly. So he can’t walk, nor can he fly. In fact he can’t even live. This is a completely illogical creature which never could have existed. And that is why no fossils have been found, for imaginary, logically impossible creatures do not leave fossils in the rocks.