Metatarsal torsion in humans and footwear type

Abstract

AbstractMetatarsal torsion has been hypothesized to be a plastic trait that can be influenced by the type of shoes worn in human populations. Wearing stiff‐sole shoes tend to result in narrower feet and higher longitudinal arches. These modifications are expected to translate into less torsion of the hallucal metatarsal but greater torsion of the four lateral metatarsals. In addition, there is some evidence that women have higher arches than men, so women are expected to have greater torsion of the lateral four metatarsals. To test these hypotheses, this paper compares men and women from two archaeological populations, Amerinds and Eurocanadians, that are documented to have worn very different shoe types, soft moccasins for the former and hard‐sole leather shoes or wooden clogs for the latter. First, we test for sexual differences within both populations, and, second, we compare the two populations. Our results show no significant differences between men and women. The similarity in torsional values for males and females is explained by the very small arch height difference documented in modern populations, a difference that is likely too small to translate into significantly different torsional values. However, the two populations had significantly different torsional values in the direction expected from the effect of wearing stiff‐sole shoes for all metatarsals except the second. The lack of differences of the second metatarsal is explained by its “keystone” position in the transverse arch of the foot; the foot shape modification brought about by wearing stiff shoes does not alter the orientation of the second metatarsals base, only raising it higher. As a consequence, torsional values for that metatarsal do not differ despite arch height differences. This study shows that metatarsal torsion values, at the population level, can inform on the type of footwear worn by past populations.