Virtual reconstruction of the Le Moustier 2 newborn skull.. Implications for Neandertal ontogeny

Here we present a virtual skull reconstruction of the Le Moustier 2 neonate based on high-resolution computed tomographic data of the delicate original fragments. In the first step, the digital fragments were assembled based on anatomical criteria. If parts were missing on one side, or were better preserved on one side than the other, we used the software Avizo to reflect them across a midsagittal symmetry plane. Missing parts of the braincase were estimated based on complete reference crania using geometric morphometrics, so as to estimate endocranial volume (EV).When we compare our reconstruction of Le Moustier 2 to modern human neonates, we find that many morphological characteristics that separate Neandertal adults from modern human adults are already established at the time of birth. Neandertal features can already be detected in the shape of the orbit, the projection of the midface, the relative size and shape of the nose, the nasal bones, and the shape of the mandibular notch. The shape differences between Le Moustier 2 and modern human neonates in the cranial base are extremely subtle. Around the time of birth modern humans and Neandertals have very similar endocranial shapes and volumes. Our EV estimates for Le Moustier 2 range between 408–428 cc.Our reconstruction of Le Moustier 2 shows that most facial differences between modern humans and Neandertals develop prenatally as they are already established at the time of birth. Most shape differences in the braincase between modern humans and Neandertals, however, develop after birth. Our reconstruction of Le Moustier 2 therefore supports the notion that modern humans and Neandertals reach similar adult endocranial capacity through different postnatal ontogenetic pathways.