PAPER ANTHROPOLOGY; CRIMINALISTICS Esperanza Guti  errez-Redomero, 1 Ph.D.; Juan A. Quir os, 2 M.Sc.; Noemí Rivaldería, 1 M.Sc.; and María C. Alonso, 3 Ph.D. Topological Variability of Fingerprint Ridge Density in a Sub-Saharan Population Sample for Application in Personal Identification ABSTRACT: 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; there- fore, a ridge density of 14 or less for both areas (ulnar and radial), support an origin sub-Saharan versus Spanish population. KEYWORDS: forensic science, forensic anthropology, fingerprints, dermatoglyphics, ridge density, sub-Saharan, Spanish The study of dermatoglyphics involves analyzing the epidermal ridges found on the surface of the palms, soles, fingers, and toes of all primate species, including humans (1). Dermatoglyphics have been used extensively in bioanthropology, genetics, and evolutionary studies to characterize populations, to analyze the nature and origin of human variability, to assess population structure, and for interpopulation microdifferentiation (2–5). Dermatoglyphics are polygenic characteristics with a possible limited environmental influence in the first few months of embryonic life (6,7). Although some methodological and genetic questions remain unresolved (4,8,9), a detailed history of the study of dermatoglyphics in human populations has demon- strated the usefulness of the information obtained from these characteristics in understanding the evolution and genetic struc- ture of human populations (10–12), in characterizing syndromes and diseases (6,13–17), and in personal identification in the field of forensic science (18–25). The formation of epidermal ridges occurs very early on in prenatal development, between the 10th and 16th week of gesta- tion: by the sixth month, the dermal papillae ridges are consid- ered fully developed (26–31). Once formed, and in the absence of lesions, these ridges will remain essentially unchanged throughout the life of the individual. Thus, ridge number is inde- pendent of age, and ridges tend to increase in size rather than in number as the body in general, and hands and feet in particular, grow (32–34). Nevertheless, age is a factor which affects finger- print recognition, as previous studies have shown that the elderly population has a higher chance of a mismatch compared with the younger population (35). Although numerous studies have been carried out on the dermatoglyphics of human populations, some of their inherent characteristics have received more attention than others. Thus, features such as main pattern type, pattern intensity index or ridge count have been widely studied (see bibliographies in 36–38), whereas other features, such as the minutiae (7,19,20,39–44, among others) or epidermal ridge breadth have received compar- atively less attention, despite being of considerable interest due to their direct relevance in personal identification. Epidermal ridge breadth or thickness is determined by two parameters: (i) ridge width, and (ii) distance between ridges, and is a character- istic which presents topological, finger, and gender variability as well as differences between populations (1,15,45–50). Recently, some studies have explored the forensic applications of this feature for inferring the gender of an individual from fingerprints of an unknown origin (51–55). Fingerprint recognition is one of the most widely used biometric systems and its use has also extended to personal authentication and government-to-citizen applications. Finger- print recognition systems must be capable of handling finger- prints and palmprints from a diverse range of demographics. However, neither the impact of gender on such systems nor the possible differences among human populations have received much attention from the research community (50,56). Therefore, the aim of this study was to analyze topological and bimanual 1 Departamento de Zoología y Antropología Física, Instituto Universitario de Investigaci on en Ciencias Policiales, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain. 2 Unidad Orgánica de la Policía Judicial de la Guardia Civil, Granada, Spain. 3 Departamento de Matem aticas, Instituto Universitario de Investigaci on en Ciencias Policiales, Universidad de Alcal a, Alcal a de Henares, Madrid, Spain. Received 23 July 2011; and in revised form 30 Jan. 2012; accepted 11 Feb. 2012. © 2013 American Academy of Forensic Sciences 1 J Forensic Sci, 2013 doi: 10.1111/1556-4029.12092 Available online at: onlinelibrary.wiley.com