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New Insights into the Evolutionary Trade-offs of Hip Width in Women
A collaborative research effort by integrative biologists from the University of Texas, Western Washington University, and Columbia University Irving Medical Center has uncovered significant findings regarding the benefits and drawbacks of both wide and narrow hips in women. Their recent study, published in the journal Science, examined hip structure in connection with various physical attributes, particularly those influencing pregnancy and childbirth, among a sample of 31,000 individuals listed in the UK Biobank.
For a long time, evolutionary theorists have grappled with what is referred to as the obstetrical dilemma. As human brain size increased during evolution, researchers noted that human hips became narrower, presenting a challenge: wider hips are essential for delivering larger-headed babies. This new study probes how evolutionary mechanisms have addressed this quandary by focusing on hip and pelvic floor anatomy.
The pelvic floor is composed of a network of muscles situated at the lower part of the abdomen, crucial for supporting the organs above it. Dysfunction in this area can lead to complications such as vaginal or uterine prolapse, incontinence, and challenges during labor.
Analyzing data from the UK Biobank, the research team identified critical correlations. Women with wider hips experienced fewer complications during childbirth; however, they also faced challenges with mobility and exhibited higher incidences of pelvic floor dysfunction and hip osteoarthritis.
Conversely, women with narrower hips demonstrated improved abilities in walking and running, yet they encountered a heightened risk of complications during delivery. They were also more prone to back pain and knee osteoarthritis compared to their wider-hip counterparts.
Interestingly, the study found no correlation between hip width and the duration of pregnancy. However, it was noted that women with wider hips generally had a propensity to give birth to babies with larger head sizes. The researchers also observed that most individuals exhibit pelvic asymmetry.
More information: Liaoyi Xu et al, The genetic architecture of and evolutionary constraints on the human pelvic form, Science (2025). DOI: 10.1126/science.adq1521
Citation: The obstetrical dilemma: Large-scale study explores evolutionary trade-offs of wide vs. narrow hips (2025, April 11) retrieved 11 April 2025 from https://phys.org/news/2025-04-obstetrical-dilemma-large-scale-explores.html
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