Are human heads getting larger?

I am responding to the intriguing PNAS article by Mitteroecker et al. (1), “Cliff-edge model of obstetric selection in humans.” My understanding is that the authors believe that Caesarean section births will allow fetuses with larger heads to survive, thus allowing our species to evolve larger heads. This is an interesting hypothesis but, as an obstetrician, I find some areas of concern. Mitteroecker et al. (1) suggest that head size has increased recently because of the number of Caesarean sections being performed for cephalopelvic disproportion (CPD). However, I do not find any reference in the Mitteroecker et al. report that shows that, indeed, newborn head size has increased. On … [↵][1]1Email: richard{at}population-matters.org. [1]: #xref-corresp-1-1