{
  "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.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Anthropology, University College London, London, UK. nicole.tamayo@ucl.ac.uk",
    "Hominin Origins Research Group, Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, Cerdanyola del Vallés, Spain. nicole.tamayo@ucl.ac.uk",
    "Institute of Evolutionary Medicine, University of Zurich, Zurich, Switzerland. nicole.tamayo@ucl.ac.uk",
    "Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Freiburg im Breisgau, Germany",
    "Institute for the Evolutionary Origins of Human Behavior, Kyoto University, Inuyama, Japan",
    "Department of Health and Rehabilitation Sciences, Program of Physical Therapy, Slippery Rock University, Slippery Rock, PA, USA",
    "Department of Ecology and Evolution, School of Life Sciences, University of Sussex, Falmer, UK",
    "Department of Anthropology, University College London, London, UK. l.betti@ucl.ac.uk"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 6,
  "authors": [
    {
      "affs": [
        0,
        1,
        2
      ],
      "name": "Nicole Torres‐Tamayo",
      "orcid": "0000-0003-2504-3886"
    },
    {
      "affs": [
        3
      ],
      "name": "Stefan Schlager",
      "orcid": "0000-0001-6493-9250"
    },
    {
      "affs": [
        4
      ],
      "name": "Eishi Hirasaki",
      "orcid": "0000-0001-7849-1936"
    },
    {
      "affs": [
        5
      ],
      "name": "Timothy D. Smith",
      "orcid": "0000-0002-6883-8964"
    },
    {
      "affs": [
        6
      ],
      "name": "Todd C. Rae",
      "orcid": "0000-0002-4010-5945"
    },
    {
      "affs": [
        7
      ],
      "name": "Lia Betti",
      "orcid": "0000-0003-2895-9718"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/by40518fgbrvb.bib",
  "cited_by": 5,
  "doi": "10.1038/s41559-026-03102-5",
  "fulltext_url": null,
  "id": "by40518fgbrvb",
  "issns": [
    "2397-334X"
  ],
  "landing_url": "https://doi.org/10.1038/s41559-026-03102-5",
  "language": "en",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1105|Primate Behavior and Ecology"
    ]
  ],
  "openalex": "W7166513638",
  "pdf_url": "https://www.nature.com/articles/s41559-026-03102-5.pdf",
  "pmcid": "PMC13541611",
  "pmid": "42373910",
  "published": "2026-06-29",
  "publisher": "Nature Portfolio",
  "ris": "https://research.draconitic.com/paper/by40518fgbrvb.ris",
  "sources": [
    {
      "first_seen": "2026-11-08T13:20:45Z",
      "native_id": "W7166513638",
      "source": "openalex",
      "url": "https://doi.org/10.1038/s41559-026-03102-5"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "openalex:1105|Primate Behavior and Ecology",
      "subfield": "ecology"
    }
  ],
  "title": "Comparative primate analysis shows that humans are not unique in having a tight cephalopelvic fit at birth",
  "title_text": "Comparative primate analysis shows that humans are not unique in having a tight cephalopelvic fit at birth",
  "type": "peer-reviewed",
  "updated_at": "2026-11-10T13:21:07Z",
  "url": "https://research.draconitic.com/paper/by40518fgbrvb",
  "venue": "Nature Ecology & Evolution",
  "versions": []
}