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 Lamarck on Contingency 
If it is true that in the case of birds the lungs are pierced through and the hair changed into feathers as a result of their habit of rising into the air, I may be asked why bats have not also feathers and pierced lungs. I reply that it seems to me probable that bats, which have a more perfect organization than birds, and hence a complete diaphram to impede the swelling of their lungs, have not been able to pierce them through nor to swell themselves out with air sufficiently for that fluid even by an effort to reach the skin and so to give to the horny matter of the hair the faculty of branching out into feathers. Among birds, in fact, air is introduced as far as the hair bulbs; changing their bases into quills and compelling this same hair to break up into feathers; an event which cannot occur in the bat, where the air does not penetrate beyond the lung.
- (Lamarck, 1802 p.76)

In a footnote in his 1802 book Zoological Philosophy, Jean Baptiste Lamarck makes this interesting statement. His fundamental mecahnism for evolution - fluids moving through the body to areas of activity and enlarging the most active parts of an organism (with children inheriting the changes that occured in their parents) has been wholy discredited. This statement, however, indicates that he understood that with evolution comes history, and with history come contingent choices. Birds followed one path to flight. Bats, given their different evolutionary history, and different resulting anatomy, could not follow the same path.

Today, we would wholy disagree with Lamarck's mechanism for exactly why birds have feathers and bats don't, but we would wholy agree that the underlying reason is their divergent evolutionary histories.

Sources: Lamrack, 1802. For a discussion of bat wings and bird wings see a comparative vertebrate anatomy text such as: Hildebrand, 1988

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Date Created: 8 Aug 1999
Last Updated: 4 Dec 1999