- Titre du projet
- Solving the evolutionary puzzle of human childbirth
- Descriptif du projet
- This project addresses one of the most persistent puzzles in human evolution. Humans are unique among the great apes in experiencing a tight fit between the birth canal and neonatal head size (Rosenberg, 1992), occasionally leading to obstructed labour and foetal or maternal death. Until recently, the most likely explanation for our species’ obstetric difficulties was the ‘obstetrical dilemma’ hypothesis (Washburn, 1960), whereby the tight human birth canal evolved as a compromise between two opposing selective pressures: the need for a narrow, compact pelvis for efficient bipedal locomotion and the need for a spacious birth canal for delivering a particularly large-brained neonate. In the last decade, however, a series of empirical locomotion studies have challenged the assumption that a wider canal leads to less efficient locomotion, leaving open the question of what alternative selective pressure could be limiting the size of women’s pelvic canal. The objective of our study is to answer this question by testing the hypothesis that erect posture, and the resulting need of the pelvis to support abdominal organs and the pregnant uterus, could be constraining the size of the birth canal. Humans have evolved a unique combination of obligatory bipedal locomotion, fully erect posture and large-brained neonates, all factors that are likely to have affected the evolution of the pelvis, but other primates share some of these characteristics: some species have a largely orthograde posture (e.g., vertical clingers, brachiators), and some species give birth to large neonates. Humans are also not unique in experiencing a tight fit between the foetus and the birth canal. By taking a wide, comparative approach across primate species, we will be able to test whether orthograde posture, especially in combination with a relatively large foetus, can explain smaller birth canals and obstetric difficulties in humans and other primates.
Travaux réalisés par la plateforme AST-RX
