An assessment of the late Middle Pleistocene occipital from Apidima 1 skull (Greece)

Abstract

Recent papers have sparked an ongoing debate on the taxonomic adscription of the late Middle Pleistocene fossil skulls from Apidima (Greece). There is general agreement that the more complete skull Apidima 2 is a member of the Neandertal lineage. However, the evolutionary significance of the anatomy of Apidima 1 is unclear. While de Lumley et al. (2019; CNRS Editions) saw both skulls as belonging to the same deme, Harvati et al. (2019; Nature 571:500) argued that Apidima 1 is the earliest evidence of Homo sapiens in Eurasia. In order to assess the morphological affinities of this fossil skull, we performed both qualitative analyses and a 3D geometric morphometric (3D GM) analysis of twelve 3D landmarks (Asterion, Lambda, Inion) and a curve of semilandmarks along the upper occipital squama of Apidima 1 with a comparative sample of Homo. At the external side of its occipital bone we found some but not all the morphological features classically recognized as Neandertal derived, e.g. a smooth suprainiac fossa and a weak bilaterally protruding transverse occipital torus. Geometric morphometric analyses reveal that Apidima 1 appears in the morphospace close to primitive H. erectus specimens, whose plesiomorphic configuration of the Apidima 1 is mostly expressed in its low and wide occipital; a condition, nonetheless, also found in other Neandertals. All together, we do not find support for the hypothesis that Apidima 1 is the earliest evidence of Homo sapiens in Europe. The presence of Neandertal apomorphic qualitative features together with the existence of primitive occipital among H. neanderthalensis populations points to a Neanderthal adscription for Apidima 1. We believe Apidima 1 may be a brachycephalic female variant of the Neandertal genetic pool. If this interpretation is correct, Neandertal lineage may encompass more anatomical variation than yet realized.