Why do humans get bunions? Or carpal tunnel syndrome? Separate research led by two Case Western Reserve University students recently published in the journal Evolution, Medicine, and Public Health, have proposed that these uniquely human maladies are understandable in the context of human’s singular adaptation—walking on two legs. This approach to better understanding the historical underpinnings of disease is known as evolutionary medicine, an approach that frames the patterns of human disease within an evolutionary and adaptive context.
Studying evolutionary medicine allows researchers to track how human health has changed over time and how our unique adaptation of walking on two legs has affected our health, including such common ailments as back problems, fallen arches and difficulty during childbirth.
Comparing skeletons of humans and primates from the Hamann-Todd Osteological Collections at the Cleveland Museum of Natural History, two recent publications by Case Western Reserve University students and faculty provide evidence that the ancient adoption of bipedality increases the risk of two other additional common health problems that are exacerbated by our modern activities.
Carpal tunnel syndrome is a debilitating nerve condition that can result in pain or loss of sensation and affects our ability to do everyday tasks such as typing, buttoning a shirt or holding a pencil. Althea (Belle) Perez, a recent graduate from the Department of Biology, discovered that the relative decrease in size and change in orientation of the pisiform bone of the wrist in humans, compared to primate wrists, exclusively predisposes humans to the pain and numbness associated with carpal tunnel syndrome.
A similar examination of bones in humans and primates was led Pierre Tamer, a second year medical student at CWRU, to identify important evolutionary changes in the human foot that predispose humans to hallux valgus, commonly known as a bunion. His research helped emphasize the reorientation of the first metatarsal in humans as a fundamental determinant of how our foot muscles contracts differently than in other primates that have a thumb-like grasping. This risk is exacerbated by wearing narrow shoes that predispose humans to development of bunions and the associated symptoms, which include pain, imbalance and falls—especially in older adults.
The students worked with Scott Simpson, professor of anatomy.