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Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma

Ricklan, SJ; Decrausaz, S-L; Wells, JCK; Stock, JT; (2021) Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma. American Journal of Human Biology , 33 (1) , Article e23451. 10.1002/ajhb.23451. Green open access

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Abstract

Objectives: The “obstetrical dilemma” hypothesis assumes that the modern human female pelvis serves two discrete functions: obstetrics and locomotion. We investigate whether these differing functions create observable patterns of morphological covariation and whether those patterns differ by height, weight, and age. This allows evaluation of evidence for canalization and phenotypic plasticity relevant to obstetric and locomotor function among a living female population. / Methods: Landmarks (N = 86) were collected and inter‐landmark distances were calculated (N = 36) on the pelvis and proximal femur of CT scans of living women aged 20 to 90 years (M = 93) receiving a routine CT scan. Partial least squares and relative SD of eigenvalues analyses were used to evaluate integration overall and within locomotor and obstetric modules, respectively. Ordinary Least Squared regression was used to evaluate scaling relationships between inter‐landmark distances and height, weight, and age. / Results: The obstetric pelvis was significantly less internally integrated than the locomotor pelvis. Many obstetric measurements were constrained in absolute terms relative to height; shorter women had relatively larger birth canal dimensions, and several key obstetric dimensions showed relative freedom from height. Lower weight women had some relatively larger obstetric and locomotor dimensions. Regarding age, younger women showed a few relatively larger outlet dimensions. / Conclusions: This study suggests that the obstetric pelvis and the locomotor pelvis function are morphologically distinct, with the obstetric pelvis showing relatively greater flexibility. These relationships between relative constraints support the hypothesis that the modern female pelvis shows evidence of both canalization and phenotypic plasticity in obstetric and locomotor structures.

Type: Article
Title: Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/ajhb.23451
Publisher version: https://doi.org/10.1002/ajhb.23451
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > UCL GOS Institute of Child Health
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > UCL GOS Institute of Child Health > Population, Policy and Practice Dept
URI: https://discovery.ucl.ac.uk/id/eprint/10105602
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