Activity-related sexual dimorphism in Alaskan foragers from Point Hope: Evidences from the upper limb

Ipiutak (100BCE-500CE) and Tigara (1200 - 1700CE) are two populations from Point Hope, Alaska. As commonly observed in forager communities, it may be expected males and females to have been involved in markedly different daily activities. Nevertheless, activity-related sexual dimorphism in these populations has been scarcely studied. Using humeral diaphyseal cross-sectional properties and forearm rotational efficiency, which are activity-dependent characteristics, we aim to assess differences between sexes and discuss what activities could have triggered them. Our results suggest that in Ipiutak males and females did not differ meaningfully in their cross-sectional properties. Conversely, in Tigara males had a greater rigidity of the entire humeral diaphysis than females, which suggests the existence of greater relative activity levels and more physically demanding tasks, possibly related to hunting activities. Concerning the differences between sexes in the forearm rotational efficiency, in Tigara females rotational efficiency in elbow flexion is maximal in a more supinated position than in males, which leads to an improvement of efficiency in those stages related to manipulation, and so improves the manipulative capacities of the upper limb. These differences in efficiency are caused by a more proximally oriented humeral medial epicondyle in females, which is thus confirmed to be a good feature to assess differences in labor. Therefore females in Tigara probably performed in a daily basis household activities, such as hide processing and other manipulative labors. In Ipiutak, the analysis of forearm rotational efficiency did not reveal differences between sexes. Overall, the results suggest that division of labor in Ipiutak was not as marked as in Tigara, where upper limb skeletal structure supports the idea that both sexes were involved in different daily activities. Nevertheless, the generalized lack of results in Ipiutak could be due to the small sample size, and thus interpretations should be considered with caution.