MadSci Network: Genetics

Re: Is tongue-rolling a genetic or learned trait?

Date: Wed May 13 17:48:03 1998
Posted By: Christopher Carlson, Grad student Genetics
Area of science: Genetics
ID: 891173241.Ge

	Well, I checked OMIM (Online Mendelian Inheritance in Man) which is a 
database of traits and the known genetics thereof.  Here's the address:


	Here's my interpretation of the summary given there: the answer is 
still a little unclear, although evidence against a genetic basis is 
mounting.  The original paper describing dominant inheritance was published 
by a very respected geneticist (Sturtevant 1940), but the follow up paper 
by Martin (1975) found little evidence for a genetic basis.   Martin 
studied the concordance rate in twins, which is also a classic study design 
for inheritance patterns.

	Given the lack of consensus in the literature, here's my opinion.  I 
seem to recall spending a while trying to figure out how to roll my tongue, 
back in the first grade.  Eventually I figured it out.  Therefore the trait 
is definitely learned, even if the capacity for rolling is inherited.  

	Further evidence for a learned basis of tongue gymnastic ability is the 
cloverleaf tongue.  My ten year old brother in law introduced this one to 
me: try rolling your tongue, and then roll the tip back on itself.  If you 
can roll your tongue, with a little practice this will make the end of your 
tongue a W or "cloverleaf" shape.  Unless you learn this trick from 
someone, I doubt you'd ever discover it by yourself.  

	However, the fact that you can learn to do tricks with your tongue 
doesn't rule out a genetic basis for the ability as well.  My mother 
definitely cannot roll her tongue, no matter how she tries.  Perhaps she 
didn't learn at a young enough age, or perhaps her genetics prevent her 
from doing it.  At this point I'd say the issue is unresolved, although 
trending toward a learned basis.  

	Chris Carlson  


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