Re: Why are taste buds clustered in different parts of the tongue?

There is no known developmental peculiarity that results in the
distribution of taste buds in humans.  Presumably the system has been
optimized over evolutionary history - but the rationale for the 
distribution has not been studied in detail.

In a medline search of 1439 papers from 1963 to 1998 that mention taste
buds, 28 discuss fetal development, 82 discuss distribution, and 34 discuss
sour taste.  None of these studies test advantages/disadvantages of altered
taste bud distribution.

For your interest, I've listed a few of the recent findings that might
interest you:

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taste buds are functional at or before birth in dogs
 Ferrell F., Neuroscience & Biobehavioral Reviews.  8(2):175-83, 1984
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human taste bud density is highest at the tip (116 tb/cm2 with a range from
3.6 to 514 among subjects at tip vs. 25.2 tb/cm2 (range: 0-85.9) in the mid
region. )
Miller IJ Jr., Anatomical Record.  216(4):474-82, 1986 Dec.
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A G-protein linked receptor, gustducin may be the principal mediator of
both bitter and sweet signal transduction
Wong GT.  Gannon KS.  Margolskee RF.   Nature.  381(6585):796-800, 1996 Jun 
27.
Margolskee RF. Bioessays.  15(10):645-50, 1993 Oct.
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