MadSci Network: Genetics

Re: Is tongue rolling, curling and folding definately inherited?

Date: Tue Mar 23 16:43:38 2004
Posted By: Alex Brands, Post-doc/Fellow, Biological ciences, Lehigh University
Area of science: Genetics
ID: 1076310105.Ge

When I read the question, I was in the same camp as your partner, but thought that 
tongue curling may be a recessive trait (which could explain your child’s talent).  So 
I looked around for information on this, and found a surprising answer:  Tongue 
curling is not a simple genetic trait.  

There has not been a lot of research done on this, but the evidence that exists 
strongly indicates that this is not a simple genetic trait.  Most convincing is a study 
done by Philip Matlock in 1952 that finds just over 20% of identical twins in the 
study (7 out of 33) are discordant for this trait.  That means one twin can curl their 
tongue while the other cannot.  Another study by N. G. Martin  (J. of Heredity 
66:179-180, 1975) found that 29% (8 out of 28) of identical twins are discordant for 
this trait.

Disturbingly, I found several web sites that proclaim matter-of-factly that the ability 
to curl ones tongue is a simple dominant trait.  I remember, as do my colleagues, 
reading this very thing in biology textbooks.  This looks like a case of “well 
everybody knows that, it must be true”.  So, your partner is incorrect about tongue 
rolling, but don’t be too hard on him, he probably learned it in school!

I found only one tenuous reference for tongue folding (Hsu, T. C. : 
Tongue upfolding: a newly reported heritable character in man. J. Hered. 39: 187-
188, 1948.) that apparently describes tongue folding as a recessive trait.  
Recessive traits can skip generations, and the people who do not show the trait can 
be “carriers”.  That means two people who can’t fold their tongue could have a child 
who is able to fold their tongue.

Here’s a couple web sites that summarizes the data:

I hope this relieves the conflict.


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