What is the genetic origin of 'clubbed thumbs'? Which ethnic groups can get it? Is it linked to anything?

Question

Clubbing of the thumbs is a genetic trait which leads to shorter, wider, stubbier thumbs. The nail is usually quite broad and a short. famous celebrities with clubbed thumb include Megan Fox and Anne Heche.

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Answer 1

Clubbed thumb(s) was once a sign or royalty & is most common among the royality & nobility of Europe.  Probably due to their extensive inbreeding over centuries.

Answer 2

eating red meat i guess and cracking the thumbs also and having a low heart beat and more stuff

Answer 3

We always referred to it as "Farmer's Thumb" because that is the family name and it is a common trait in the family.  If it makes any difference, the family is of Irish/French/Cherokee descent.

Answer 4

I've known one person with clubbed thumbs and he was half Indian, but I doubt there's a higher rate in a certain ethnic group, it seems random.  Does the correlation between linking it with royalty in England mean it's from inbreeding?  It is of course genetic, with most likely random mutation as its origin, but no studies on that or prevalence seem to have been conducted as of yet.