Civil Whorl

Anyone know the prevalence of double parietal hair whorls?

When my first child, Alex, was an infant, I read a study about a possible relationship between the rotational direction of one’s hair whorl and one’s handedness. When I checked Alex’s, I discovered he actually has two. I have no idea what that might portend for his handedness, but he seems to be pretty strongly a righty. My second child, Joel, has a counterclockwise whorl and seems to be a left-leaning ambi. Number three, Lily, has a clockwise whorl and is almost certainly a righty.

I was discussing all this with my parents and sister recently when I made an interesting observation. I asked my father to lend his head for a simple demonstration of whorl rotation, and I was startled to see that he has a double whorl pattern like Alex! Lucky for him, though, his rotate away from each other, so he doesn’t have the cowlick problems Alex has. As far as I know, he’s always been strongly right-handed, but he does have a rather unorthodox two-footed driving style.

Look familiar?

I’ve tried to find out more about the genetics of this seemingly rare phenotype, but I haven’t been successful. I’ve learned that the link between whorls and handedness is less certain than I’d thought. I haven’t been able to find reliable numbers for the prevalence of double whorls, but it appears to have an approximate upper limit of 5%. Can anyone help me find something more certain?