How do you evolve a BAT?

This is meant to be a little light-hearted, not strictly scientific (so "Is it science" is probably the best forum):How do you evolve a BAT?First a brief history:The (currently) oldest known bat is this guy ... the 54 million year old "new" bat fossil:Which we can compare to this modern bat skeleton:And we can note certain differences (longer tail, claws on all hand fingers) and certain similarities (long finger bones, shorter hind legs that forelegs).The current thinking on bat evolution can be summarized by these two articles:(1) http://www.si.edu/Encyclopedia_SI/nmnh/batfacts.htm

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Evidence for bat-like flying mammals appears as far back as the Eocene Epoch, some 50 million years ago; however, the fossil record tracing bat evolution is scanty. Based on similarities of bones and teeth, most authorities agree the bat's ancestors were probably insect eating placental mammals, possibly living in trees, and likely the same group that gave rise to shrews and moles.

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(2) Insectivore-like mammals, Tiny teeth and their enigmatic owners

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However, there are only small differences between the teeth of bats and those of certain Paleocene insectivores, including members of the Nyctitheriidae and an unnamed genus known from Germany and Rumania (38, 39, 40). Some of these animals may turn out to be ancient bats when they become better known, especially when skeletons are found. This would not be surprising from the point of view of molecular studies which place the orders Chiroptera and Lipotyphla close to each other on the family tree of mammals (7, 8).

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Thus we will set a starting point for our game of evolving a bat with a shrew-like animal living when the Yucatan Meteor kindly removed large predatory dinosaurs from the paths of evolution. But what is shrew-like?This is a modern tree shrew:

It just finished eating an insect that it caught and held between its front paws (similar behavior to squirrels and racoons).This is a modern diving water shrew:
FIGURE 3. A diving American water shrew (Sorex palustris)
(From: "Olfaction: Underwater 'sniffing' by semi-aquatic mammals" by Kenneth C. Catania, Nature 444, 1024-1025(21 December 2006), doi:10.1038/4441024a)

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This semi-aquatic species has water-repellent fur and is the smallest mammalian diver.

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Flight evolution in birds and the "WAIR" theory: Wing-Assisted Incline Running and the Evolution of Flight - curiously the wing beating pattern is different in juvenile birds than in flying adults:

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This hypothesis is based upon the observation of ground-dwelling birds that use wing-assisted incline running (WAIR). This type of locomotion is not often seen, usually occurring in very short bursts when a bird attempts to escape a predator. By rapid flapping of the wings, the bird can create enough traction to run up a vertical surface.

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Kenneth Dial has been studying WAIR for several years. In the current study he tested chukar partridges (and them’s good eatin’!) from first-day hatchlings to adult birds. He found that even newly hatched birds will climb ramps using their wings to paddle along and will leap off a drop flapping the wings to (poorly) control descent. Older birds become more adept at climbing in this manner and controlling descent on the other side of the ramp, until adult birds are able to climb a vertical surface and take off into powered flight.

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Dial found the the orientation of the wingbeat remains constant from day 8 to adulthood and is different from that used in flight, and proposes that this wingbeat used in WAIR is a fundamental wing-stroke that predates and is ancestral to flight.

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That would be a transitional behavior between running and flying, one with a clear survival advantage, as well as one that is observed in existing birds as they develop from down covered arms to fully feathered wings. Curiously this behavior does not include trying to glide on the developing wings.Such flapping while falling to control descent is seen in many young birds, Wood Ducks would be an example many could be familiar with.Now the fun part begins:Stipulations:(1) Why does the bat hang up-side-down: how did this evolve and why would it be beneficial? Did this behavior evolve before flight?(2) How does the webbing between the fingers evolve? We do NOT see this formation in flying squirrels and sugargliders, probably because it interferes with other necessary use of front paws for climbing.(3) If you start with an aquatic shrew to get webbing, how do you get back in the tree and hang up-side-down, and why do you lose the rear feet webbing?(4) How does wing flapping evolve if you start with gliding? Conversly how are you going to have WAIR behavior in tree shrew?Let the games begin.Enjoy.

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Thread copied to the How do you evolve a BAT? thread in the Miscellaneous Topics in Creation/Evolution forum, this copy of the thread has been closed.