For several decades, the simultaneous evolution of the pelvis to support bipedal locomotion and a larger cranium was the leading hypothesis for the selective co

For several decades, the simultaneous evolution of the pelvis to support bipedal locomotion and a larger cranium was the leading hypothesis for the selective constraints on birth timing (known as the obstetrical dilemma). Recently, however, a hypothesis that focuses on metabolism and efficient energy transfer from mother to child through the placenta vs feeding has become popular (the EGG hypothesis. Yes, that is the actual acronym from the literature).