Covariation between human pelvis shape, stature, and head size alleviates the obstetric dilemma

Barbara Fischer, Philipp Mitteroecker

    Publications: Contribution to journalArticlePeer Reviewed


    Compared with other primates, childbirth is remarkably difficult in humans because the head of a human neonate is large relative to the birth-relevant dimensions of the maternal pelvis. It seems puzzling that females have not evolved wider pelvises despite the high maternal mortality and morbidity risk connected to childbirth. Despite this seeming lack of change in average pelvic morphology, we show that humans have evolved a complex link between pelvis shape, stature, and head circumference that was not recognized before. The identified covariance patterns contribute to ameliorate the "obstetric dilemma." Females with a large head, who are likely to give birth to neonates with a large head, possess birth canals that are shaped to better accommodate large-headed neonates. Short females with an increased risk of cephalopelvic mismatch possess a rounder inlet, which is beneficial for obstetrics. We suggest that these covariances have evolved by the strong correlational selection resulting from childbirth. Although males are not subject to obstetric selection, they also show part of these association patterns, indicating a genetic-developmental origin of integration.

    Original languageEnglish
    Pages (from-to)5655-5660
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America (PNAS)
    Issue number18
    Publication statusPublished - 5 May 2015

    Austrian Fields of Science 2012

    • 106045 Theoretical biology


    • Correlational selection
    • Evolution
    • Morphometrics
    • Obstetric dilemma
    • Pelvis

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