Comparative primate analysis shows that humans are not unique in having a tight cephalopelvic fit at birth
Torres-Tamayo, Nicole (Institut Català de Paleontologia Miquel Crusafont)
Schlager, Stefani (University Medical Center Freiburg)
Hirasaki, Eishi (Kyoto University)
Smith, Tim D. (Slippery Rock University)
Rae, Todd C. (University of Sussex)
Betti, Lia (University College London)

Date:	2026
Abstract:	Human childbirth is regarded as uniquely difficult among primates, due to a tight cephalopelvic fit thought to result from an evolutionary trade-off between adaptations to bipedal locomotion and increasing brain size. This impression, however, may be an artefact of past adoption of anthropocentric measurements that underestimate birth challenges in non-human primates. Here we re-evaluate cephalopelvic proportions using species-specific three-dimensional data of the pelvic inlet along with neonatal cranial dimensions from a broad sample of extant primates. Results reveal that maternal body size is a key factor to consider. A tight cephalopelvic fit occurs in species with proportionately larger neonates, smaller pelves or a combination of both. The latter is the case in humans, producing the tightest fit among extant apes, but a similar combination of factors explains much more extreme cephalopelvic proportions in other species. Our findings reveal a diversity of obstetrical dilemmas across primates.
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Published in:	Naure Ecology & Evolution, June 2026

DOI: 10.1038/s41559-026-03102-5

23 p, 3.0 MB

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Institut Català de Paleontologia Miquel Crusafont (ICP)
Articles > Research articles
Articles > Published articles