Climbing influences entheseal morphology in the humerus of mice: An experimental application of the VERA methodology

Objectives

When studying hominin skeletal remains, anthropologists commonly assume that the morphology of entheses (muscle and tendon attachment sites) is influenced by physical activity patterns during life. Here, we use samples of mice from a prior experiment (Siegel & Jones 1975] American Journal of Physical Anthropology 42:141–144) to test this assumption. Specifically, we investigate the effects of habitual climbing on entheses of the humerus using a recently developed protocol for analyzing entheseal morphology called the “Validated Entheses-based Reconstruction of Activity” (VERA) method.

Materials and Methods

In the original experiment, young mice were raised for approximately 9 weeks in one of two experimental conditions: a cage designed to limit locomotion to terrestrial quadrupedalism over a flat surface (n = 22), or a cage designed to impel animals to cling to a suspended wire mesh apparatus and limit their locomotion to climbing (n = 21). We μCT-scanned the humeri of these mice and used the VERA method to assess the morphology of the deltoid tuberosity, greater tubercle, lesser tubercle, and supinator crest.

Results

Significant differences in entheseal morphology were detected between climbers and non-climbers when using both multivariate statistics to assess all entheses simultaneously and univariate statistics to assess each enthesis individually.

Discussion

Our results provide new support for the general use of entheseal morphology for inferring hominin physical activity patterns in the past. Furthermore, based on our results, we propose that analyzing entheseal morphology using the VERA method may be a promising strategy for future research on the importance of climbing in hominin locomotor evolution.