There’s an odd twist to human physiology not seen in any other primate 0 that makes giving birth more complicated for our species. Now, a study using biomechanical modelling on gait and posture has provided some insights into this long-standing mystery.

The narrow shape of the human birth canal is kinked at the inlet, so that contractions of the mother must rotate the baby’s big brain and wide shoulders nearly 90 degrees to fit into the pelvis.