Simulations indicate that extinct Australopithecus hominins faced childbirth challenges similar to modern humans, with high pressures on their pelvic floors risking tears. Researchers analyzed pelvises from three Australopithecus species to model these forces. The findings highlight potential pelvic floor disorders in these early ancestors.
Childbirth posed significant risks for Australopithecus, early hominins who lived in Africa between 2 million and 4 million years ago. These ancestors walked upright, adapted to trees, and possibly used stone tools, potentially linking them to the Homo genus.
A team led by Pierre Frémondière, a midwife at Aix-Marseille University in France, examined the unique oval shape of the Australopithecus birth canal—wide from side to side but narrow front to back. This differs from chimpanzees' transverse-narrow canals and humans' more circular ones. To assess labor stresses, the researchers simulated births using three pelvises: from Australopithecus afarensis, Australopithecus africanus, and Australopithecus sediba.
They adapted a three-dimensional MRI image of a pregnant woman's pelvic floor to fit these ancient pelvises and modeled a baby passing through. The simulations revealed forces of 4.9 to 10.7 megapascals on the pelvic floor, comparable to the 5.3 to 10.5 megapascals in human births. Frémondière noted, “We show that Australopithecines are quite similar to modern humans. If they had lots of deliveries, probably they would have a greater risk of pelvic floor disorder.”
In humans today, such forces contribute to tears and disorders like incontinence or prolapse, affecting about 1 in 4 women. Lia Betti at University College London praised the study's use of multiple pelvises and human comparisons for robustness but urged caution. Differences in Australopithecus muscle resilience remain unknown, and one simulation failed to show proper fetal rotation, suggesting gaps in the model. Betti added, “The problem is just we do not have a huge amount of evidence,” with only three pelvises available and none from earlier hominins.
Frémondière agreed, stating, “I think that we are just at the beginning of this kind of study.” The research appears in The Anatomical Record (DOI: 10.1002/ar.70173).