2D:4D finger length ratio in the Chuvashian population

In a sample of Chuvashians (803 males and 738 females) we evaluated the mean values of index finger to ring finger (2D:4D) ratio, the contributions of phalanges and metacarpals to the 2D:4D ratio, and the symmetry between right and left 2D:4D ratios. Age, sex, anthropometric data and radiographs of both hands were collected. Each hand was visually classified on a radiograph as either Type 1 - index finger was longer than ring finger; Type 2 - equal; or Type 3 - index shorter than the ring finger. The following measurements (1) from the mid-point of the base of the proximal phalanx to the mid-point of the tip of the distal phalanx; and (2) from the mid-point of the base to the mid-point of the tip of the metacarpal were obtained from the index and ring fingers. Visual classification was significantly associated with the measured 2D:4D length ratio. Women had a higher prevalence of Type 1 and Type 2, but lower prevalence of Type 3 ratio in both hands. Men had smaller measured 2D:4D phalangeal, metacarpal and ray (combined) ratios than women. Symmetry between the right and left hand measured 2D:4D ratios were significant in phalangeal (r=0.657, p<0.001), metacarpal (r=0.638, p<0.001), ray (r=0.682, p<0.001) ratios and visual classification types (contingency coefficient=0.559, p<0.001). No sex dimorphism was found between the right and left hands. Correlations between age and visual classification were significant on both sides before and after adjustment for sex. This result is probably a sign of a secular trend in the Chuvashian sample and the study should be replicated in other samples.