Fluctuation and directional asymmetry of the oppositely orientated finger ridge counts in Bulgarians.

In a sample from Northeast Bulgaria (500 males, 500 females) fluctuating and directional asymmetries of the radial and ulnar finger ridge-counts were studied, each sex separately and finger-by-finger. Neither the ridge counts nor their fluctuating asymmetries show any considerable sex difference. In contrast, the curves of the ulnar and radial directional asymmetries, each of them being similarly distributed over the digits in both sexes, are contrasted in males and females. One interpretation is that the sex chromosomes exert a considerable effect upon the mediolateral developmental gradients and so cause a set of well expressed sex differences in the directional asymmetries of the ulnar and radial finger ridge-counts.