Bipedalism and human birth: The obstetrical dilemma revisited


  • Karen Rosenberg,

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    • Karen Rosenberg is Associate Professor of Anthropology at the University of Delaware. She is a paleoanthropologist who has worked on fossils in Europe, the Near East and Eastern Asia. Her research interests are in the origin of modern humans and the evolution of modern human childbirth.

  • Wenda Trevathan

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    • Wenda Trevathan is Associate Professor of Anthropology at New Mexico State University. Her major research interests are the evolution of human female reproductive behavior, including sexuality, pregnancy, childbirth, and menopause. Her major publications include Human Birth: An Evolutionary Perspective and articles on menstrual synchrony, sexuality, and evolutionary medicine.


…adaptation to bipedal locomotion decreased the size of the bony birth-canal at the same time that the exigencies of tool use selected for larger brains. This obstetrical dilemma was solved by delivery of the fetus at a much earlier stage of development. (Washburn1)

…there can be no doubt that many of the obstetrical problems of Mrs. H. Sapiens are due to the combination of a narrower pelvis and a bigger head in the species. (Krogman2)