An Analysis of the Functional Significance and Sexual Dimorphism of the Neandertal Mastoid Process

This study examines the functional significance and sexual dimorphism of the Neandertal mastoid process. The mastoid process is identified as a part of the Posterior Cranial Complex which includes the nuchal and occipital planes, and a portion of the basicranium as well as the mastoid region of the temporal bone.

In order to draw conclusions regarding the functional significance and sexual dimorphism of the mastoid process, a number of multivariate statistical techniques are applied to a modern human sample; the Larson Site Arikara.

The examination of the morphological features of the Neandertal posterior cranial vault (a relatively long, low and broad cranium, a broad, rugose and horizontally oriented nuchal plane, a large occipitomastoid crest, and a supposedly small and nonprojecting mastoid process) shows that this morphology provides an extensive and optimally oriented area of attachment for the powerful muscles that act to counterbalance and provide force for the utilization of the relatively massive Neandertal dento-facial complex. It is demonstrated that the function of the mastoid process in Neandertals as well as modern hominids, is to provide a point of insertion for the sternocleidomastoid muscle and to provide an additional area of attachment for the nuchal musculature. It is hypothesized that, in Neandertals, the occipitomastoid crest is developed to a greater extent than in modern hominids in order to provide even more area for the attachment of the increased nuchal muscle mass of Neandertals. This large caudally projecting crest masks the projection of the mastoid process, thus fostering the illusion of a small nonprojecting Neandertal mastoid process.

This study also demonstrates that it is possible, with some reservations, to determine the sex of individual Neandertal crania utilizing the dimensions of the mastoid process. Two methods are presented that produce nearly identical results.