Robusticity of Hand Phalanges: Relevance to the Origin of the Altai Neanderthals

The cross-sectional geometry of middle phalanges of hand digits 2-4 in five European and Asian Neanderthals (La Ferrassie 1, Kiik-Koba 1, Okladnikov 2 and 5, and Chagyrskaya 16-3-12) and five Cro-Magnons (Kostenki 14, Telmanovskaya TII 175 and TII 173, Sungir 1, and Abri Pataud 26227) was assessed by means of microtomography. Both taxons reveal a wide range of individual variability in their indices of inner robusticity. Both the most robust and the most gracile variants in Neanderthals were recorded in the Altai (Okladnikov and Chagyrskaya caves, respectively), which confirms previous observations about the high morphological diversity among Neanderthals in that area, and the presence of at least two morphological variants among them. In European Upper Paleolithic Homo sapiens, inner phalangeal robusticity is generally higher than in Neanderthals, attaining medullary stenosis in the Kostenki 14 male. Neither sex nor age nor even mechanical stress appear to have affected robusticity. Hyper-robust variants were recognized in both Cro-Magnons and Neanderthals of supposedly hybrid origin. Genetic studies suggest that Kostenki 14 belonged to an ancestral European metapopulation that had absorbed some Neanderthal admixture. The ancestors of the Altai Neanderthals, on the other hand, included not only Denisovans but also early anatomically modern humans before their migration to Siberia. Extreme phalangeal robusticity in Middle and Upper Paleolithic Eurasians, then, might be a legacy of early anatomically modern humans.