Variability in ridge density in a sub-Saharan population sample was studied by counting ridges in three fingerprint areas (two distal regions, radial and ulnar, and one proximal region) on the epidermal surface of the distal phalanx. Study material was obtained from the fingerprint impressions of 100 male sub-Saharan subjects aged between 18- and 48-years old. The results were compared with those obtained from a Spanish population sample. Sub-Saharan males presented lower ridge density than Spanish males in the distal regions (radial and ulnar) of all fingers, whereas differences in the proximal region were only observed on some fingers. Using the differences observed between these populations, the likelihood ratio for inferring membership of one of the populations from a fingerprint of unknown origin was calculated; therefore, a ridge density of 14 or less for both areas (ulnar and radial), support an origin sub-Saharan versus Spanish population.

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Topological Variability of Fingerprint Ridge Density in a Sub‐Saharan Population Sample for Application in Personal Identification

Fingerprint ridge density (RD) is known to vary according to sex and population, and such variation can be used for forensic purposes. The aim of this study was to analyze the fingerprint RD of two samples of the Argentinean population in order to assess their topological, digital, bilateral, sexual, and population differences for subsequent application in the inference of sex. Data were collected from the fingerprints of 172 individuals from the Buenos Aires province and 163 from the Chubut province. RD was assessed for three different count areas for all 10 fingers of each individual. In both sexes and both samples, significant differences among areas were obtained, so that radial-RD>ulnar-RD>proximal-RD. Females presented greater RD than males in all areas and on all fingers. Regarding population differences, no significant differences were found between the Buenos Aires and Chubut samples (except for proximal RD in males). However, both samples showed RD significantly different from that of the Jujuy province. The application of Bayes' theorem allowed for the identification of an RD threshold for discrimination of sexes in these Argentinean samples. In conclusion females consistently exhibit narrower epidermal ridges than males, which may evidence a universal pattern of sexual dimorphism in this trait that can be useful in forensics in the identification of individuals.

Fingerprint ridge density in the Argentinean population and its application to sex inference: A comparative study

Assessment of the methodology for estimating ridge density in fingerprints and its forensic application.

We have analyzed dermatoglyphic finger patterns in a Spanish Basque population (841 males and 911 females). Bimanual and sexual comparisons have been carried out by means of contingency analysis. The results in the Basque population are compared with those of other Spanish populations, based on univariate (chi 2 contingency test and Student's t-test) and multivariate (principal components analyses) statistical methods. Bilateral distribution asymmetry and sexual dimorphism were observed in the Basque sample. The results of the chi 2 test for pattern types in males and females show statistically significant differences between the Basques and other Spanish populations, with the exception of the males from El Bierzo. Comparing populations with regard to the Pattern Intensity Index, the differences observed are much lower; therefore, this confirms what other authors have suggested regarding the limited usefulness of indexes in populational comparisons. In the Caucasian variation range of pattern types, Basques are located in the high part with regard to arches, in the low part with regard to whorls and radial loops, and in an intermediate part in relation to ulnar loops and overall pattern intensity. Results of the multivariate comparisons show which populations are more or less distant from the Basque population and which variables are significant in contributing to these population relationships.

Digital dermatoglyphics in the Basque population: univariate and multivariate comparison with other Spanish populations.

Digital dermatoglyphics of an indigenous sample of 87 males and 101 females from the Urola Valley in the Spanish Basque Country are compared with those from the nine other Basque valleys previously analyzed. In both sexes of the Urola Valley, there is a very high frequency of radial loops; the mean found in this valley extends the range of variation for South European-Mediterranean populations, and it is in the superior limit of all Caucasian populations. There are bimanual and sex differences in the frequencies of whorls and loops. Contrary to what occurs normally in populations, in the Urola Valley the frequency of whorls is higher in females and the quantitative value of digital patterns is lower in males. The results of this study show the existence of heterogeneity among valleys for digital trait frequencies and for finger ridge count, and this heterogeneity is more marked in females.

Quantitative and qualitative finger dermatoglyphics in the Basque Valley of Urola, Spain.

Hand clasping and arm folding have been analysed in 286 males and 455 females of the Basques. The results are compared with those from other Spanish populations. Examination of the association between hand clasping and arm folding shows a strong correlation between the right type of one and the left type of the other.

Hand clasping and arm folding in the Basque population.

Despite all the papers on the classification of dermatoglyphic features, there is no definitive in sight yet. With this work we intend to contribute to adapt the subclassification of spiral monocentric whorls to their biologic nature. The results in this work show that clockwise whorls on the right hand match counter-clockwise ones on the left, and counter-clockwise spirals on the right are joined together with clockwise on the left. We propose the building of two new subclasses of spiral monocentric whorls to replace the traditional ones in order to conserve the bilateral identification of these pattern types.

Subclassification of spiral monocentric whorls

In a sample from the Biscaian Basque population, we studied the incidence of pattern types in fingers and the parallelism between the frequencies for the orientations of whorls (Wr, Ws, Wu) and the other pattern types (Lr, A, Lu). We reaffirm the importance of clarifying pattern types according to their orientation, which is of general use in the case of loops but less easily applied to whorls.

Parallelism between the frequencies of differently oriented whorls and other pattern types in Basque population

Fingers pattern types of a sample of 834 unrelated individuals (353 males and 481 females) from the Biscaian Basque valleys of Uribe, Gernika, Markina, Arratia and Durango were subjected to correspondence analysis. The results show that there are different local subpopulations with regard to these dermatoglyphic traits. The importance of whorls in the separation of these populations is observed. Isolation may have been the factor differentiating between the valleys.

C. M. Lostao

Papers

Digital dermatoglyphics in the Basque population: univariate and multivariate comparison with other Spanish populations.

Hand clasping and arm folding in the Basque population.

Subclassification of spiral monocentric whorls

Parallelism between the frequencies of differently oriented whorls and other pattern types in Basque population

Correspondence analysis of digital pattern types in Basque valleys