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.
Radioulnar contrasts (numerically: differences) between ridge counts of individual fingers of the human hand have been identified as promising features in respect to prenatal signalling. In this study, we compared the results of a meta-analysis of intersex differences in radioulnar contrasts between published mean values of dermatoglyphic ridge counts on the fingers of the hand (calculated from the higher RC of each finger) with intersex differences obtained from radioulnar contrasts already calculated at the individual level.Searching the NCBI-PMC, ScienceDirect databases, and archival resources, we found a total of 273 dermatoglyphic studies (after merging duplicates in databases). However, only 11 of those studies were suitable for meta-analysis after application of all selection criteria, including our own four studies. Considering the effort spent in searching for articles, we were able to find very few studies that published statistical parameters of ridge counts by individual finger and that would thus be suitable for studying contrasts between fingers. When statistical parameters have been published for individual fingers, they did not represent the descriptions of all ridge counts from the radial and ulnar sides of the fingers (i.e., 10 values on each hand), but only the ridge count with the higher value is selected for each finger (i.e., 5 values on each hand) at the individual level. The meta-analytically obtained sex dimorphism (contrasts between the mean values of the ridge counts) are virtually indistinguishable from the dimorphism from the contrasts calculated at the individual level (means of the contrasts). However, the step of selecting one (higher) ridge count from each finger blurs the dimorphism and makes interpretation of the sex differences difficult. The results cannot then be compared with those obtained from the complete set of all ridge counts on the fingers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.