According to a new study, chimpanzees, like humans, must contend with a confined bony birth canal when giving birth. In humans, the problem was exacerbated by our unique form of upright walking since ...

3D simulation of the birth canal of chimpanzees with (B) the fetal head in a fully extended position, the typical head alignment in apes, and (C) the fetal head in a fully flexed position, the usual ...