Kiik-Koba 2 and Neandertal axillary border ontogeny

Abstract

The significance of morphological variation in the axillary border among Pleistocene and recent humans has been considered for nearly a century, with the high frequency of the dorsal sulcus pattern in the Neandertal lineage receiving particular attention. Although usually considered an epigenetic trait, or phylogenetic marker, the variation has also been related to functional demands on the shoulder region. The Kiik-Koba 2 infant Neandertal scapula, as one of the developmentally youngest ones known, exhibits a smooth ventral surface, a ventral displacement of the lateral margin, a prominent dorsal bar, and a dorsolateral sulcus along the border. This configuration is best seen as an incipient dorsal sulcus pattern, and given the young age-at-death of Kiik-Koba 2, supports the epigenetic trait interpretation of the morphological variation.