ArticleProceedings. Biological sciences2018
Human variation in the shape of the birth canal is significant and geographically structured.
Article in Proceedings. Biological sciences, 2018. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 31 papers, 2 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
31 citing papers in PubMed, 2 syntheses or guidelines pooled it, 95 citations in OpenAlex.
- Maternal postures for fetal malposition in late pregnancy for improving the health of mothers and their infants.The Cochrane database of systematic reviews · 2024Pooled it
- Evolutionary Theories and Men's Preferences for Women's Waist-to-Hip Ratio: Which Hypotheses Remain? A Systematic Review.Frontiers in psychology · 2019Pooled it
- Conflict, Constraint, Cooperation, and Allocation: A Plural Evolutionary Architecture for Human Reproductive Paradoxes.American journal of biological anthropology · 2026Article
- Childbirth experience among different Iranian ethnic groups: a cross-sectional study.BMJ open · 2026Article
- Pelvic shape predisposes for pelvic organ prolapse: a geometric morphometry study.Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology · 2025Article
- Racial differences in the levator ani muscle and levator hiatus in individuals of reproductive age.American journal of obstetrics and gynecology · 2025Article
- Gradual exacerbation of obstetric constraints during hominoid evolution implied by re-evaluation of cephalopelvic fit in chimpanzees.Nature ecology & evolution · 2024Article
- Comparison of the Vaginal and Labial Dimensions of Ethnic Chinese and Western Nullipara.International urogynecology journal · 2024Article
- Ethnic background as a risk factor for permanent brachial plexus birth injury: A population-based study.Acta obstetricia et gynecologica Scandinavica · 2024Article
- Updating of pelvimetry standards in modern obstetrics.Scientific reports · 2024Observational
- Magnetic resonance imaging pelvimetric measurements as predictors for emergent cesarean delivery in obstructed labor.European journal of obstetrics & gynecology and reproductive biology: X · 2023Article
- There is an obstetrical dilemma: Misconceptions about the evolution of human childbirth and pelvic form.American journal of biological anthropology · 2023Review
- Changes in plasticity of the pelvic girdle from infancy to late adulthood in Homo sapiens.Scientific reports · 2023Article
- Gynaecoid Pelvis among Female Patients Attending Department of Radiology of a Tertiary Care Centre: A Descriptive Cross-sectional Study.JNMA; journal of the Nepal Medical Association · 2023Article
- Take it to the limit: The limitations of energetic explanations for birth timing in humans.Evolution, medicine, and public health · 2023Review
- Genomes of extinct hominins and human reproductive evolution.EXCLI journal · 2023Article
- Evaluation of dual-energy X-ray absorptiometry compared to magnetic resonance imaging for collecting measurements of the human bony pelvis.American journal of human biology : the official journal of the Human Biology Council · 2022Article
- Neonatal head circumference by gestation reflects adaptation to maternal body size: comparison of different standards.Scientific reports · 2022Article
- Squatting, pelvic morphology and a reconsideration of childbirth difficulties.Evolution, medicine, and public health · 2022Article
- Variability and the form-function framework in evolutionary biomechanics and human locomotion.Evolutionary human sciences · 2022Review
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
2 authors at 2 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
The human birth canal shows a tight fit with the size of the neonate, which can lead to obstetric complications. This is not the case in other apes, and has been explained as the outcome of conflicting evolutionary pressures for bipedal locomotion and parturition of a highly encephalized fetus. Despite the suggested evolutionary constraints on the female pelvis, we show that women are, in fact, extremely variable in the shape of the bony birth canal, with human populations having differently shaped pelvic canals. Neutral evolution through genetic drift and differential migration are largely responsible for the observed pattern of morphological diversity, which correlates well with neutral genetic diversity. Climatic adaptation might have played a role, albeit a minor one, with populations from colder regions showing a more transversally oval shape of the canal inlet. The significant extent of canal shape variation among women from different regions of the world has important implications for modern obstetric practice in multi-ethnic societies, as modern medical understanding has been largely developed on studies of European women.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.