Research

My primary academic interest is the comparative anatomy, evolution, and development of the skeleton. In particular, I study the interactions between soft tissue structures such as ligament, tendon, and even neural tissue, with bone.

Research

My primary academic interest is the comparative anatomy, evolution, and development of the skeleton. In particular, I study the interactions between soft tissue structures such as ligament, tendon, and even neural tissue, with bone.

Tendon and Ligament Insertions

The interface between ligament/tendon and bone is important to archaeologists and paleontologists in that it often leaves behind “muscle scars” used to interpret the activity patterns of past species or populations. They are also clinically important because they are often the site of injury. These sites are biologically important in that they are the site of energy dissipation during movement of the musculoskeletal system. However, the formation of these sites, and what we can learn by studying their shape and size, remains understudied. My research addresses the comparative morphology of ligament insertion sites across mammalian taxa to assess how these sites respond to changes in body mass and locomotion, and activity level. These studies will aid in the interpretation of archaeological populations, and have additional implications for clinical research. In order to study these sites effectively, I use traditional morphometric and gross anatomical approaches, as well as histological methods.

Evolution of the Mammalian Knee

My past and current research focuses on the knee and the ways it has changed in the evolutionary shift from arboreal quadruped to biped. I focus on the human knee in terms of its novelty, as well as its shared primate evolutionary past- and how both of these aspects leave it vulnerable to injury. I used quantitative polarized light microscopy to demonstrate that animals with a smaller range of motion have subdivisions of the ACL that are farther apart from one another than animals with a greater range of motion, yet are more uniform in collagen fiber orientation. These data inform a prominent debate in current orthopedic surgery- whether double-bundle ACL reconstruction is more appropriate than the standard single-bundle reconstruction- as well the anthropological literature on the evolution of the human knee.

I also explore the proximate structures of the ACL, such as the lateral meniscus. Humans have a unique lateral meniscus in that ours has two attachment points to the tibia- one anterior, and one posterior. It is common for paleoanthropologists to describe traits unique to humans as adaptations to bipedality, and the posterior meniscotibial ligament is no exception. However, I examined the possibility that this trait is a consequence of the geometry of our knee and found that humans and orangutans have each independently evolved similar but unique morphologies in the lateral meniscus, despite their widely divergent locomotion patterns. I argue that this supports a developmental hypothesis in which the shape of the menisci is a consequence of the pattern formation of the condyles, and reassess the fossil evidence of its presence in several australopithecine fossils.

Basicranial Anatomy

In addition to my work on the postcranium, I also conduct research using cranial morphometrics as they relate to brain size and other factors. A traditional hypothesis in physical anthropology posits that the foramen magnum is located more anteriorly in humans as an adaptation to bipedality- i.e., in order to balance the head atop a bipedal spine. My research tested this hypothesis against the hypothesis that foramen magnum position is the result of developmental interactions between the brain and cranium. I tested this hypothesis first in bats, which do not vary with regard to locomotion, but do vary with regard to brain size. I was able to use relatively simple linear morphometrics to demonstrate that neocortex size is a determining factor in foramen magnum position in bats. I expanded this research to primates, rodents, and marsupials, and expanded my hypotheses to include masticatory size and the size of the auditory bullae. My paper on the position of the foramen magnum in rodents, marsupials, and primates is in the May 2016 volume the Journal of Human Evolution.