My research focuses on understanding human and non-human primate evolution by examining patterns of evolutionary covariation in the skeleton. While this research draws from evolutionary biology and anthropology, it has practical applications: skeletal evolution directly impacts human and animal health and well-being. My research is relevant to current questions in evolutionary medicine, medical anthropology, veterinary science, and human and comparative anatomy.
THE EVOLUTION OF OBSTRUCTED LABOR
Obstructed labor, defined as a situation in which the fetus’s head or body is unable to pass through the birth canal due to mechanical obstruction, is common in human populations, with real medical and social consequences. This subject, sometimes referred to as the “Obstetric Dilemma,” has been a frequent topic of interest in biological anthropology for over 70 years, but very few studies have directly tested primate – human or non-human – pelves for evidence of obstetric selection and even fewer have incorporated the cranium in these analyses.
My dissertation research applied methods from evolutionary quantitative genetics to assess whether the pelvis and cranium were co-evolving in ways that suggested obstetrics may have played a role in the evolution of these skeletal elements in humans and in a broader range of primates. This research was generously funded by the National Science Foundation, the Richard Gilder Graduate School Collections Study Grant, the University at Buffalo’s Mark Diamond Research Fund, and the Morris E. and Lucille Opler Dissertation Research Scholarship. Additional support to expand the scope of this project and develop teaching materials for university-level courses has been provided by the Western Washington University PILOT Project Grant Program.
CRANIAL INTEGRATION & ORBITAL EVOLUTION
Increasingly forward-facing eyes and increased reliance on vision are considered characteristic of primate evolution. This has been investigated via the skeletal morphology of the cranium, particularly the orbital region and the anterior frontal bone. Additionally, the skeletal morphology surrounding the orbit is important in investigations of human evolution due to the distinct morphology of the frontal bone in hominins.
However, the eyes and their surrounding skeletal scaffolding are situated near other highly important biological structures, the masticatory region, the nasal region, and the forebrain, all of which may influence (or be influenced by) the evolution of the orbit. My postdoctoral work in the Primate Evolution Lab at Western Washington University focuses on analyzing how the morphology of the orbit covaries with other regions of the cranium and how this region may impact overall cranial evolution and patterns of cranial integration across catarrhine primates. This work is funded by the National Science Foundation (PIs Dr. Tesla Monson and Dr. Marianne Brasil).
EVOLUTIONARY PROCESSES OVER ONTOGENY
While methods from evolutionary quantitative genetics are increasingly applied in biological anthropology to better understand how evolution has shaped the primate skeleton, these investigations are typically restricted to adult morphology. This limits our understanding of how changing evolutionary processes affecting primates across ontogeny (growth) may impact adult morphology. Preliminary research has indicated that strong stabilizing selection characterizes the early non-human hominid cranium, while neutral evolutionary processes better characterize the adult cranium in each module. Future research will both expand taxonomic representation and explore different methods of testing evolutionary constraint and flexibility in primates across different age stages to better understand how the combined forces of evolutionary pressures and ontogenetic patterns combine to influence the adult skeleton.
SAMPLE COMPOSITION, DATA STANDARDIZATION, & THEIR IMPACT ON MORPHOMETRIC ANALYSES
How biological samples are chosen and how data is collected, standardized, and analyzed is an ongoing, important topic of conversation in evolutionary biology and anthropology. Minor changes in sample construction or data transformation can create mathematical artifacts that may lead even the most careful researcher to misleading conclusions. In an effort to better understand how these choices may affect the outcome of research, I test different sample compositions and methodological choices to better understand the impact these factors have on patterns of trait covariance. A recent project on size adjustment methods on evolutionary quantitative genetics analyses, is under review at the American Journal of Biological Anthropology. I am also currently working with Hannah Oliver, a PhD student at the Buffalo Human Evolutionary Morphology Lab, to examine how morphological differences between captive and wild Macaca fascicularis – likely arising from differences in environmental rather than genetic factors – may affect research reliant on variance-covariance matrices.
MARIANNE J. COOPER, Ph.D. 