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�������� Assistant Professor of Anthropology Marianne Brasil worked as a co-author on a paper published in one of the world’s most prestigious journals, Science, on April 11. 

Titled “The genetic architecture of and evolutionary constraints on the human pelvic form,” the paper is a comprehensive study of the genetic architecture of the human pelvis and weighs in on central hypotheses about human pelvic evolution. 

Brasil and her team’s paper breathes new life to an age-old question about human evolution by providing empirical data that opens the field to new research directions and discussions.

Brasil and her co-authors at The University of Texas at Austin and Columbia University used a deep-learning model to extract seven pelvic phenotypes—including three measurements of the birth canal—from X-ray images of over 31,000 people. The study resulted in two major findings: it identified 180 positions in the genome that have an influence on pelvic anatomy, and it tested the long-standing obstetrical dilemma hypothesis.

“Before this study, the genetic basis of the human pelvis was largely unknown,” Brasil said. “We didn’t really have a good sense of which genes are contributing to the anatomy that we see. And that's not just in humans; that’s across vertebrate animals.”

“This hasn’t been done before largely because we haven't had the datasets and methods available to do this kind of study,” Brasil said. “I’m excited to see the discussion this is going to generate within the field.”

The "obstetrical dilemma," which was first coined in 1960, refers to the evolutionary conflict between the demands of childbirth and locomotion: a larger birth canal is better for birthing our large-brained babies, but a narrower pelvis is better for efficient upright bipedal walking. This hypothesis has been at the center of decades' worth of research regarding human evolution and the role different factors play in the evolution of the pelvis. However, recent methods and dataset developments, like the UK Biobank used in this study, allowed Brasil and her team to approach the 60-year-old question in a new way.

“We wanted to test this obstetrical dilemma idea but also look at some of the traits having to do with pelvic floor health to see if that’s also playing a role in shaping our human pelvis,” Brasil said.

With this approach, Brasil and her team were able to identify some factors they found to be linked to different birth canal shapes, ultimately supporting and expanding the obstetrical dilemma hypothesis. They found that smaller birth canals were associated with an increased risk of obstructed labor, back pain, and knee osteoarthritis, whereas an increased risk of pelvic floor disease, hip osteoarthritis, and a decreased walking speed were associated with larger birth canals.

Brasil’s work on this comprehensive study on the genetic architecture of the human pelvis is one of many projects she has been involved in. From analyzing human and monkey fossils found in eastern Sudan to paleontological field research in northern Ethiopia, Brasil’s excitement for her research is something that extends far beyond her publications and actively carries into her classrooms.

“I work research into the classroom as much as I can," Brasil said. “I’ve seen how it can help students feel more of a connection to the material and makes it feel less abstract.”

As Brasil continues to work out in the field and in the classroom, she said the shared camaraderie, goals and values within the �������� community bring meaning and strength to research.

“What I appreciate is that Western emphasizes research as an active process and encourages faculty to bring their research into the classroom and to share it with students,” Brasil said. “Western doesn’t only claim to care about its students and about teaching, but it actively does. Being here, you can feel that faculty care about their students’ learning and their wellbeing, and that has definitely been one of the highlights of my first couple of years as part of the community here.”