The genetics of hand-clasping--a review and a familial study.

Hand-clasping refers to the preferential tendency for individuals to clasp the hands together. This paper reviews the previous literature on family data and twins, and reports new data. In this study about 55% of the population are left-hand-claspers, 44% are right-hand-claspers, and the remaining 1% report that they have no preference or are indifferent. Familial data suggest that hand-clasping may be under genetic control: although the data do not fit any straightforward recessive or dominant Mendelian model, they are compatible with the type of model invoking fluctuating asymmetry which has been used to explain the inheritance of handedness and arm-folding. It is possible that hand-clasping, as for example arm-folding, may be an idiosyncrasy due to or influenced by physical bilateral differences in the hands. All data together are suggestive of a genetic basis, although environmental influences are also evident.