Radioulnar contrasts in fingerprint ridge counts: Searching for dermatoglyphic markers of early sex development

Abstract

Objectives Using prenatally fixed dermatoglyphics features as markers of prenatal sex development is limited due to insufficient knowledge on their sex differences. This study aims to examine more thoroughly sex differences in radioulnar contrasts. Methods Fingerprints of 360 females and 331 males from four samples of different ethnic backgrounds (Czechs, Slovaks, Vietnamese and Lusatian Sorbs) were studied. On both hands, finger ridge counts were recorded, and all possible radioulnar contrasts were computed as a difference between ridge count at a radial position minus ridge count at a respective ulnar position on the hand. Radioulnar contrasts with population‐congruent and numerically large dimorphism were selected and the dimorphism of the selected radioulnar contrasts was then tested using nonparametric analysis of variance. Results Greater dimorphism of radioulnar contrasts occurred on the right hand than on the left hand. Population congruent direction and relatively strong dimorphism (Cohen’s d greater than 0.3) was found in six radioulnar contrasts on the right hand, all of which involved the radial ridge count of the 2nd finger. Of these, the highest average dimorphism was observed for the difference between the radial ridge count of the 2nd finger and the ulnar ridge count of the 4th finger (2r4u contrast), where the average effect size from all four population samples was comparable to a published average effect size of the 2D:4D finger length ratio. Conclusion We propose that 2r4u contrast of ridge counts could serve as a marker of prenatal sexual development targeting a temporally narrow developmental window.

Meta-analysis of radioulnar contrasts in dermatoglyphic ridge-counts between individual fingers

“…This uneven distribution is due to sparsely published separate average ridge counts for individual fingers for each sex. Based on results of Polcerová et al (2019;2022) and we decided to explore the consistency of radioulnar gradients among multiple populations and possible sexual dimorphism in those radioulnar gradients via meta-analytical methods summarized in Borenstein et al (2009).…”

“…The purpose of this study is to perform a meta-analysis of dermatoglyphic studies dealing with RCs and to determine whether radioulnar contrasts of published parameters of individual ridge counts are comparable to results (Polcerová et al 2022) based on primary data of RCs of individual fingers. First, we had to find out what the published RC data are and whether it is possible to find data separately for each RC of each finger.…”

“…First, we had to find out what the published RC data are and whether it is possible to find data separately for each RC of each finger. If such data existed in the literature, the next step was to collect such studies and use their data to evaluate the radioulnar contrasts of the RCs and compare them with the results found by analysis of the primary individual data (Polcerová et al 2022).…”

“…Archival resources were represented by three samples (collected in 1948, 1976, and 1989): sample of adult population of Lusatian Sorbs, sample of exchange Vietnamese students and historical sample of adult Czech population used in diploma thesis of ; for further information about samples please ref. Polcerová et al (2022).…”

“…In particular, for RC, one of the most important quantitative dermatoglyphic features, it has been shown in recent years that not only the sum of RC values (TFRC) is important, but also the differences between individual fingers carry significant information (Kahn et al 2008;2001). Some radioulnar contrasts (differences) between RCs on different fingers show systematic sex dimorphism (Polcerová et al 2022), so we can think of them as markers of prenatal sexual differentiation, similar to the 2D:4D ratio of finger length (cf. Jantz 2021).…”