Recent fossil discoveries have provided increasing evidence that early human ancestors engaged in a variety of forms of locomotion, combining some type of terrestrial bipedal walking with varying degrees of arboreal behavior. It has been difficult to interpret these differences, however, in part because we have very limited modern analogies to compare with the fossil forms. The goal of the present study is to determine how differences in locomotor behavior in modern gorillas are related to differences in skeletal characteristics, in order to better reconstruct the locomotion of early humans from their fossil remains.
Gorillas constitute a group of closely related species and subspecies that have recently diversified, both genetically and ecologically. Eastern mountain gorillas inhabit high altitude environments that encourage very little arboreal climbing behavior, while western lowland gorillas inhabit rainforest environments where climbing is a common activity. There also is a geographically intermediate group of gorillas that inhabits both high and low elevations and that shows a mixture of locomotor behaviors. Using museum specimens from varying gorilla populations, limb bone structural properties will be determined using computed tomography and other measurements, and compared between the different groups. It is hypothesized that limb bone strength proportions will more closely reflect differences in locomotor behavior than will other skeletal characteristics. Growth studies of western lowland and mountain gorillas also will be carried out and compared, using juvenile skeletal material from the same populations. It is known from behavioral studies that mountain gorillas undergo a change in locomotor behavior during growth, becoming less arboreal as they become older, while this is less true for western lowland gorillas. It is hypothesized that limb bone strength proportions in the two groups will be more similar in infancy and diverge thereafter.
This project will add significantly to our understanding of genetic and environmental effects on skeletal morphology and growth. It involves an international collaboration between the PI and researchers in Belgium and Finland, and provides training for two graduate students. The data generated by the study also will promote understanding of living gorilla ecology and population history, which will aid in conservation efforts for these Endangered species.