That infant head looks mighty large compared to thatnarrow birth canal. And to add to that, the baby comes out facing down andbackwards, which means mothers can do little to assist the birth, or even tountangle the baby from the umbilical cord.
According to evolutionary anthropologists, babies of theearliest humans had a 50-50 chance of coming out facing backwards. This was aresult of humans learning to walk on two feet. As the pelvis became optimizedfor walking, the birth canal developed twists and turns that meant the baby hadto rotate in order to keep the head and shoulders aligned with the widest partat all times.
And then our brains got bigger, which meant more twistsand turns and backwards-facing babies.
Some of the earliest humans learned to compensate for thedifficulty of giving birth by receiving assistance during childbirth, and thatmade a huge difference in terms of survival.
Some anthropologists think there might be an evolutionaryadvantage to having someone help you give birth, and conjecture that humanfemales who gave birth to backwards-facing babies, and females who hadassistance because they felt particularly anxious about the birth ended updoing better than females who didn’t. After all, if problems arise duringlabor, having another person around can mean the difference between life anddeath.