Northern exposure: Mandibular torus in the Greenlandic Norse and the whole wide world.

OBJECTIVES In the first issue of the American Journal of Physical Anthropology, E.A. Hooton noted the expression of Eskimoid characteristics in the Icelandic skull, one of which was mandibular torus. Our goal is to evaluate this trait in another North Atlantic population, the Greenlandic Norse. MATERIALS AND METHODS An investigation of mandibular torus was carried out on all Greenlandic Norse skeletons disinterred up to 1986 (n = 109), along with comparative samples from Iceland (n = 82), Norway (n = 98), and Denmark (n = 64). Torus expression was scored on a six grade scale with absence and five degrees of trait presence. RESULTS Greenlanders and Icelanders show extraordinarily high frequencies (65-97%) and pronounced expressions of mandibular torus. More surprising was the almost complete absence of this trait in a Danish Viking sample (9%) and a significantly lower frequency in medieval Norwegians (48%). DISCUSSION The dramatic expression of mandibular torus in the Greenlandic Norse and their contrast to related Scandinavian populations in Europe stimulated the collection of data from the literature and the database of Christy G. Turner II for 49,970 individuals in 335 populations. When plotted on a global scale, mandibular torus shows a strong clinal distribution with the highest frequencies in northern latitudes and the lowest frequencies around the equator. Although mandibular torus has some hereditary component, as indicated by family studies, the trait has a strong environmental component of variance. How factors of a northern environment, including climatic stress and dietary behavior, influence torus expression remains enigmatic.