Dynamic finite-element simulations reveal early origin of complex human birth pattern

Pierre Frémondière (1, 2) , Lionel Thollon (3, 4) , François Marchal (2) , Cinzia Fornai (5) , Nicole M Webb (6) , Martin Haeusler (5)

1 AMU SMPM EM - Aix-Marseille Université - École de maïeutique
2 ADES - Anthropologie bio-culturelle, Droit, Ethique et Santé
3 Université Gustave Eiffel
4 LBA UMR T24 - Laboratoire de Biomécanique Appliquée
5 UZH - Universität Zürich [Zürich] = University of Zurich
6 Senckenberg Research Institute and Natural History Museum [Frankfurt]

Human infants are born neurologically immature, potentially owing to conflicting selection pressures between bipedal locomotion and encephalization as suggested by the obstetrical dilemma hypothesis. Australopithecines are ideal for investigating this trade-off, having a bipedally adapted pelvis, yet relatively small brains. Our finite-element birth simulations indicate that rotational birth cannot be inferred from bony morphology alone. Based on a range of pelvic reconstructions and fetal head sizes, our simulations further imply that australopithecines, like humans, gave birth to immature, secondary altricial newborns with head sizes smaller than those predicted for non-human primates of the same body size especially when soft tissue thickness is adequately approximated. We conclude that australopithecines required cooperative breeding to care for their secondary altricial infants. These prerequisites for advanced cognitive development therefore seem to have been corollary to skeletal adaptations for bipedal locomotion that preceded the appearance of the genus Homo and the increase in encephalization.

Mots clés: Biological anthropology; Anthropology

Domaines: Sciences du Vivant [q-bio]

Pierre Frémondière, Lionel Thollon, François Marchal, Cinzia Fornai, Nicole M Webb, et al.. Dynamic finite-element simulations reveal early origin of complex human birth pattern. Communications Biology, 2022, 5, ⟨10.1038/s42003-022-03321-z⟩. ⟨hal-03838550⟩