Original communication What is the appropriate approach in sex determination of hyoid bones? Petra Urbanová, PhD, Head of Laboratory of Morphology and Forensic Anthropology a, * , Petr Hejna, MD, PhD, Head of Institute of Legal Medicine b , Lenka Zátopková, MD, Assistant Professor b , Miroslav  Safr, MD, Assistant Professor b a Department of Anthropology, Faculty of Science, Masaryk University, Brno, Czech Republic b Institute of Legal Medicine, Medical Faculty of Charles University and University Hospital Hradec Králové, Sokolská 581, 500 05 Hradec Králové, Czech Republic article info Article history: Received 9 October 2012 Received in revised form 24 May 2013 Accepted 20 August 2013 Available online 29 August 2013 Keywords: Hyoid bone Sex determination Linear discriminant function analysis Symbolic regression Geometric morphometrics abstract The hyoid bone is characterized by sexually dimorphic features, enabling it to occasionally be used in the sex determination aspect of establishing the biological profile in skeletal remains. Based on a sample of 298 fused and non-fused hyoid bones, the present paper compares several methodological approaches to sexing human hyoid bones in order to test the legitimacy of osteometrics-based linear discriminant equations and to explore the potentials of symbolic regression and methods of geometric morphomet- rics. In addition, two sets of published predictive models, one of which originated in an indigenous population, were validated on the studied sample. The results showed that the hyoid shape itself is a moderate sex predictor and a combination of linear measurements is a better representation of sex- related differences. The symbolic regression was shown to exceed the predictive powers of linear discriminant function analysis when two models based on a logistic and step regression reached 96% of correctly classified cases. There was a positive correlation between discriminant scores and an in- dividual’s age as the sex assessment was highly skewed in favour of males. This suggests that the human hyoid undergoes age-related modifications which facilitates determination of male bones and compli- cates determination of females in older individuals. The validation of discriminant equations by Komenda and  Cerný (1990) and Kindschud et al. (2010) revealed that there are marked inter-population and inter-sample differences which lessened the power to correctly determine female hyoid bones. Ó 2013 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved. 1. Introduction The human hyoid bone is known to bear sexually dimorphic features noticeable even from early stages of postnatal life. 1 Adult male hyoids are reported as significantly larger than those of fe- males and this is the same case for absolute values of the widths and lengths of the greater horns and hyoid body. 2,3 In shape, female bones are typically wider; yet, the basis of the sexual dimorphism is presumed to lie in variability of the total length than in changes of width parameters. 4 Additional sex-related differences have been described in the shape of hyoid body 5 where female bones are predominantly assigned with types characterised by rounded lower borders with the lowest corners situated closely to the midsagittal plane, whereas the male type is described as either rectangular in shape or rounded with the lowest corners placed further apart. Ultimately, the role of asymmetry has been stressed as a sexually dimorphic feature. 6 The magnitude of observed sexual dimorphism is expressed to a degree which allows hyoid bones to be used for practical purposes, i.e., as a sex predictor while assessing an individual’s biological profile from skeletal remains. To date, there have been numerous studies which have produced predictive equations for sexing hu- man hyoids. 7e9 While variable in the quality and quantity of input parameters, these studies have reported rates of accuracy ranging from 82% to 96% of correctly classified specimens. For separate anatomical elements, the rate of accuracy has been markedly lower. For instance, in the case of the hyoid body, Reesink et al. 2 reported accuracy as little as 79% for correctly classified specimens. Like for many other skeletal elements in human body, the success of sex assessment using hyoid bones is affected by the manifestation of sexually dimorphic traits within a given population, inter- population shifts in patterns of sex-related differences as well as * Corresponding author. E-mail addresses: urbanova@sci.muni.cz (P. Urbanová), HejnaP@lfhk.cuni.cz (P. Hejna), lenka.zatopkova@seznam.cz (L. Zátopková), safrm@lfhk.cuni.cz (M.  Safr). Contents lists available at ScienceDirect Journal of Forensic and Legal Medicine journal homepage: www.elsevier.com/locate/jflm 1752-928X/$ e see front matter Ó 2013 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved. http://dx.doi.org/10.1016/j.jflm.2013.08.010 Journal of Forensic and Legal Medicine 20 (2013) 996e1003