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Were Neandertal Humeri Adapted for Spear Thrusting or Throwing? A Finite Element Study

An ongoing debate concerning Neandertal ecology is whether or not they utilized long range weaponry. The anteroposteriorly expanded cross-section of Neandertal humeri have led some to argue they thrusted their weapons, while the rounder cross-section of Late Upper Paleolithic modern human humeri suggests they threw their weapons. We test the hypothesis that Neandertal humeri were built to resist strains engendered by thrusting rather than throwing using finite element models of one Neandertal, one Early Upper Paleolithic (EUP) human and three recent human humeri, representing a range of cross-sectional shapes and sizes. Electromyography and kinematic data and articulated skeletons were used to determine muscle force magnitudes and directions during three positions of spear throwing and three positions of spear thrusting. Maximum von Mises strains were determined at the 35% and 50% cross-sections of all models. During throwing and thrusting, von Mises strains produced by the Neandertal humerus fell roughly within or below those produced by the modern human humeri. The EUP humerus performed similarly to the Neandertal, but slightly poorer during spear thrusting. This implies the Neandertal and EUP human humeri were just as well adapted at resisting strains during throwing as recent humans and just as well or worse adapted at resisting strains during thrusting as recent humans. We also did not find any correlation between strains and biomechanical metrics used to measure humeral adaptation in throwing and thrusting (retroversion angle, Imax/Imin, J). These results failed to support our hypothesis and suggest they were capable of using long distance weaponry.