MadSci Network: Evolution
Query:

Re: How did the bat's wing (pentadactyl limb) evolve?

Date: Mon Jan 22 10:33:07 2001
Posted By: Jeff Otjen, Undergraduate, Molecular Biology, University of Texas at Austin
Area of science: Evolution
ID: 980027443.Ev
Message:

You are quite right in saying that the bat's wing is homologous to other 
structures like the human forearm and hand, and the whale's flipper.  Bats 
present some difficulty in the study of their evolution, however due to 
the understandable lack of fossil preservation.  Being a flying mammal, 
with very delicate structures, it is exceedingly rare to find a bat fossil 
that can tell us anything, as the thin soft membranes and bones do not 
survive until fossilization, which requires a quick burial - something a 
flying animal rarely has.  Nevertheless, in the abscence of much solid 
evidence, we can still put forward theories, and at the moment, there are 
two theories as to how the bats' wings and flight could have evolved.  The 
arborial theory says that bats probably evolved as gliding animals first, 
living in the trees and having skin flaps much like those of flying 
squirrels.  Extending and thinning the skin, along with lightening and 
exteding the bones, would give ever more control over their leaping, which 
eventually became true flight.  The cursorial theory says that bats could 
have evolved the same structures by way of running and leaping off the 
ground, perhaps into an updraft or off a cliff.  I favor the arborial 
theory, as we have evidence of a niche that can be filled by such gliding 
animals leaping from tree to tree, and we do not see any mammalian gliders 
taking a running leap.  But there may be other evidence that supports 
either theory, you will have to consult a zoological library to be 
certain.  

Good luck, and thank you for using the Mad Scientist Network!



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