Human bones were recovered in 1997 near Serra San Quirico in Ancona province (Marche, Central Italy) during archaeological excavations carried out by the Soprintendenza ai Beni Archeologici delle Marche. The site is located in a cave, 20 metres above the plane of the road, on the wall of a fluvial gorge called “Gola della Rossa”. The remains consist of a cranial vault and a few non-articulated postcranial bones, possibly belonging to the same individual. The sex diagnosis was made on the basis of morphological features of the preserved anatomical parts. According to some of these qualitative features (e.g. supraorbital region development, receding frontal profile, rounded upper orbital margin, vault thickness), the cranial vault seems to belong to a male individual; other features (e.g. frontal eminences), instead, are more typical of a female.With these data, the likelihoods were elicited by means of the Bayesian B-spline model.