Voyaging into the third dimension: A perspective on virtual methods and their application to studies of juvenile sex estimation and the ontogeny of sexual dimorphism

In contrast to the well-established and highly accurate morphological methods available for sexing adult skeletons, juvenile sex estimation is widely recognised as a difficult task that faces a series of challenges. The acquisition of 3D data, and construction of 3D models from volume or surface scans, has become increasingly common in forensic sciences, and these data offer considerable opportunity for the development and refinement of methods in sex estimation. The suitability and potential of virtual methods for juvenile sex estimation are evaluated with the aims of identifying (1) the benefits and challenges associated with virtual data and quantitative analysis of 3D models, and (2) pathways that may lead to practical improvements for sexing juveniles. The issues associated with sex estimation in juveniles are discussed and approached in the context of a framework that unifies classification results for a given trait, which provide information on its capacity to discriminate between the sexes, with the underlying patterns of dimorphism over ontogeny. Virtual collections of 3D models are suggested as integral to this framework because they enable the magnitude and mode of sexual dimorphism to be comprehensively quantified for a chosen trait or set of traits. Those data can be used to inform decisions about how to apply a method for sex estimation to maximize its success. Virtual collections, through extending the scope of analyses and impacting the way in which questions on sexual dimorphism in juveniles may be answered, are undoubtedly set to play a central role in future research.