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.