The female pelvic canal is not so well designed for giving birth compared to other primates. Therefore obstructed labour used to be a high death factor. Luckily, the introduction of Caesarean section in the fifties saved the life of many mothers and babies. Though C-section has an unexpected side effect on human evolution: newborn heads are getting bigger, while the mothers birth canals are becoming smaller.
“We predict that this weak directional selection has led to a 10 to 20 per cent increase in the rate of fetopelvic disproportion since the regular use of Caesarean sections” says lead author Dr Philipp Mitteroecker, member of the research team. "Disproportion may further increase. But I don't think that one day every baby needs to be delivered by C-sections. The selection towards larger babies is limited by the mother's metabolic capacity and also attenuated by modern medical treatment".
This study shows how a new medical technique led to an accidental evolutionary change in the human DNA. The next step might be the redesign of the female body, so the baby fits again. Losing the created evolutionary change seems to be a pity. Because who knows, maybe bigger skulls also lead to smarter children?