On Sat, 6 Nov 2004 03:31:10 +0000 (UTC), Brett Aubrey
 wrote:

>In Richard Dawkin's The Ancestor's Tale, he mentions the 50/50 split on
>Humanity's ability to curl our tongue into a tube.  Might there have been a
>reason for this trait, or its' absense?  Or is this just likely an example
>of a minor mutation that is advantageously neutral?  Or something else?  TIA
>Regards, Brett Aubrey.
>

There are a number of traits traditionally taught in intro genetics
classes that similarly seem to have absolutely no function:
    tongue rolling
    widow's peak hairline
    attached vs. free ear lobes
    hand clasping, right vs. left thumb on top
    thumb hyperextension  (hitchhiker's thumb)
    mid-digital hair
 
There are some illustrations at
http://scidiv.bcc.ctc.edu/rkr/Biology201/labs/pdfs/HumanInheritance201.pdf

The usual explanation is that these are simply anatomical
peculiarities that result from developmental processes, perhaps as
side effects (spandrels?)   It is difficult to find a trait dependent
(or at least largely dependent) on any single gene that can be seen
easily without doing biochemical or molecular biological studies.  So
these have been identified as examples.  In teaching, I call them
silly little examples of genetics.  All  "real" traits involve so many
alleles at so many loci with so many gene interactions and
environmental influences that they become too difficult to study in an
intro class.
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