Baby Steps: What 3D Scans of the Pelvic Morphology in Ugandan Chimpanzee Populations Can Reveal About Our Bipedal Origins and the 'Obstetrical Dilemma Hypothesis'
Location
PANEL: Anthropology Honors
Wilder 101
Moderator: Baron Pineda
Document Type
Presentation - Open Access
Start Date
4-25-2025 10:00 AM
End Date
4-25-2025 11:00 AM
Abstract
Why are humans, compared to other primates, born so helpless? My research tests aspects of the oldest and most widely accepted proposed explanation: The Obstetrical Dilemma (OD) hypothesis. The OD hypothesis postulates that slimmer pelvises result in more efficient bipedal movement, but with the evolutionary tradeoff that human babies must be born earlier to ensure that their heads fit through the pelvic outlet during birth. Using resources in Mary Church Terrell Main Library’s DigiLab, I created 3D scans and took obstetrically-relevant morphology measurements of pelvises of two populations of Ugandan chimpanzees, one fully quadrupedal and one whose members had frequently been observed moving bipedally. However, I found no statistically significant difference in the measured pelvic dimensions between the two populations. One explanation may be that there are confounding factors in my study, but another is that one of the central ideas of the OD hypothesis—that bipedalism is more efficient with a slimmer pelvis—is not sound.
Keywords:
Evolution, Birth, Chimpanzee, 3D Modeling
Recommended Citation
Merithew, Amelia, "Baby Steps: What 3D Scans of the Pelvic Morphology in Ugandan Chimpanzee Populations Can Reveal About Our Bipedal Origins and the 'Obstetrical Dilemma Hypothesis'" (2025). Research Symposium. 2.
https://digitalcommons.oberlin.edu/researchsymp/2025/presentations/2
Major
Anthropology
Biology
Project Mentor(s)
Amy Margaris, Anthropology
2025
Baby Steps: What 3D Scans of the Pelvic Morphology in Ugandan Chimpanzee Populations Can Reveal About Our Bipedal Origins and the 'Obstetrical Dilemma Hypothesis'
PANEL: Anthropology Honors
Wilder 101
Moderator: Baron Pineda
Why are humans, compared to other primates, born so helpless? My research tests aspects of the oldest and most widely accepted proposed explanation: The Obstetrical Dilemma (OD) hypothesis. The OD hypothesis postulates that slimmer pelvises result in more efficient bipedal movement, but with the evolutionary tradeoff that human babies must be born earlier to ensure that their heads fit through the pelvic outlet during birth. Using resources in Mary Church Terrell Main Library’s DigiLab, I created 3D scans and took obstetrically-relevant morphology measurements of pelvises of two populations of Ugandan chimpanzees, one fully quadrupedal and one whose members had frequently been observed moving bipedally. However, I found no statistically significant difference in the measured pelvic dimensions between the two populations. One explanation may be that there are confounding factors in my study, but another is that one of the central ideas of the OD hypothesis—that bipedalism is more efficient with a slimmer pelvis—is not sound.
