An Attempt at More Objective Description of Dermatoglyphic Variability

Abstract

After discussing briefly still existing uncertainties as to the mode of determination and ontogenetic formation of dermatoglyphs, the authors conclude that definitions of dermatoglyphic characters should be constructed in a way relating features of ridged skin to the morphology of anatomical regions covered by it and allowing for precise, quantitative analysis. Along these lines, quantitative characters analyzed in the present paper are constructed. The characters are: numbers of ridges on three main morphological "fields" of the palm—subdigital area (SA), hypothenar (H), and thenar (Th)—lengths of these fields, and "ridge density" on each field. The lines along which ridges are counted run approximately at right angles to ridges, and their length is determined by the size of the appropriate areas (see Fig. 1). The ridge density, as used in this paper, is a quantity inverse to ridge breadth defined by Cummins and Penrose & Loesch. Besides the above-described characters, "traditional" quantitative dermatoglyphic traits were analyzed: TRC and a-b-c-d ridge count.

As material, prints of both hands from 43 males, 44 females, and 39 children aged 3-17 years were used. The children were the progeny of 39 out of the 44 examined women, providing 39 mother-child pairs for analysis. All characters were determined on each hand, and on right-hand prints of 5 males and 5 females, taken separately five times from each individual (resulting in a total of 50 prints), measurements and countings were repeated to estimate random observational error variance (V_R see Table 1). Additionally, to obtain information on qualitative dermatoglyphic characters, the "pattern intensity" in each of the three fields was classified into one of the five categories, ranging from 0 (practical lack of patterns) to 4 (large whorls and other complex patterns).

In order to estimate the contribution of genetic and environmental factors to the variability of observed characters, a variety of methods commonly used in the genetics of quantitative traits, along with statistical analysis procedures, were applied. The study revealed that the heritability of the characters constructed for the purposes of this study is high (h² sensu lato between 0.70 - 0.94), comparable to that of Total Ridge Count (TRC), while qualitative (descriptive) traits are, at least formally, less heritable (0.3 - 0.5). There is no relation between TRC and ridge counts on palms, while the numbers of ridges on separate "morphological fields" of the palm are interrelated (Tables 5 - 9). The relation between Subdigital Area (SA) ridge count and a-d count is an artifact resulting from a very similar mode of counting the same ridges. Therefore, in further analyses, only one of these two values has been considered. The highest relationships between fields of the palm were observed in ridge density (Tables 8 and 9). Besides a-d ridge count, no relation was found between "pattern intensity" and quantitative characters (Table 12). From the estimates of "genetic polymorphism" (P_g) and "ecosensitivity" (D_e) as proposed by Henneberg and Lewicki (1978), it may be concluded that, after correcting for the variance of random observational error, quantitative dermatoglyphic characters behave in the same way as anthropometric traits of the body (weight, head length, etc.). The only exception is TRC with higher polymorphism and ecosensitivity, which probably results from a somewhat "artificial" definition of this character inflating its variance (Table 13).

The general conclusion of the present study is that ridge density is a “basic” dermatoglyphic property, ridge count results from density and size of the morphological area, while course of ridges is related to three-dimensional shape of anatomical structure they cover and is the “weakest” of the dermatoglyphic characters.