Sexual dimorphism in limb bones of ibex (Capra ibex L.): mixture analysis applied to modern and fossil data

Abstract

Estimating sex ratios of fossil bone assemblages is an important step in the determination of demographic profiles, which are essential for understanding the palaeobiology and palaeoethology of any particular species, as well as its exploitation patterns by humans. This is especially true for ibex (Capra ibex), which was a main source of food for hominids during Pleistocene times. Classical methods for determining sexual dimorphism and sex ratio, such as analyses using uni-and bivariate plots, are based on an arbitrary fixing of limits between sexes. Here we use a more robust statistical method termed mixture analysis (MA) to determine the sex of postcranial remains (long bones, metapodials and tarsals) from ibex. For the first time, we apply MA to both a modern and a fossil sample of one species, by using metric data taken from (i) a collection of present-day ibex skeletons and (ii) a Palaeolithic sample of the same species. Our results clearly show that the forelimb (humerus and radius) is more dimorphic than the hindlimb (femur and tibia) and is therefore better suited for sexing ibex. It also appears that metapodials should be used carefully for estimating sex ratios. On the basis of these results, we propose a classification of bone measurements that are more or less reliable for sexing ibex. The results of MA applied to the ibex fossil bones from the Upper Palaeolithic site of the Observatoire (Monaco) lead us to the conclusion that this assemblage consists of a majority of males. The quantitative estimations calculated by the MA make it possible to compare the size of Pleistocene and modern ibex for the whole set of variables used in this study.

Three statistical methods for sex determination in extant and fossil caprines: assessment of the Rupicapra long bones

“…Thus a generally better performance is obtained with the bones of the anterior limb rather than with those of the hind limb. These results are similar to those obtained from other caprines such as the mouflon (Monchot, 1999) or the ibex (Fernández and Monchot, 2007).…”

“…This analysis is based on the maximum likelihood method when the sample consists of several components (Monchot and Léchelle, 2002;see below). This method has been successfully applied to determine the sex ratios in several species, such as the ibex (Capra ibex), mouflon (Ovis antiqua) and cave bear (Ursus spelaeus) among others (Monchot, 1999;Quiles and Monchot, 2004;Fernández and Monchot, 2007). Finally, discriminant analysis together with character traits have been used for sexing mountain gazelle (Gazella gazella) (Munro et al, 2011).…”

Sexual dimorphism among Mesoamerican turkeys: A key for understanding past husbandry

“…Gaussian mixtures have perform well in other morphometric studies in identifying size groups (e.g. De Cupere et al, 2005;Dong, 1997;Fernández and Monchot, 2007;Monchot and Léchelle, 2002;Monchot, 1999) as well as groups based on shape (Baylac et al, 2003;Cordeiro-Estrela et al, 2006, 2008.…”

“…This topic has been widely used to characterize wild mammals hunting strategies (e.g. Fernández and Monchot, 2007;Jones, 2006;Monchot, 1999;Weinstock, 2000), the first steps of mammal domestication (e.g. Helmer et al, 2005;Vigne et al, 2012;Zeder, 2001) and economic systems of mammal husbandry (cf.…”

Disentangling long bones of foxes (Vulpes vulpes and Alopex lagopus) from arctic archaeological sites

“…;Monchot and Lé chelle, 2002;Quilè s and Monchot, 2004;Monchot et al, 2005;Fernandez and Monchot, 2007. …”