Fraggle Rocker
Staff member
It should be noted that difficulty giving birth is a phenomenon almost unique to humans, because it's the result of two evolutionary developments that conflict with each other.
Therefore there is a limit to how large a newborn human brain can be. In fact human babies are arguably more helpless than any other mammal: Baby giraffes, for example, literally "hit the ground running" and scamper away.
But we need that brain to be just as large as possible, so the baby can breathe, suckle, swallow, and perform the minimum activities necessary for survival, and nonetheless require full-time care in order to simply survive.
This is why childbirth is so difficult for humans. It's a miracle that it works at all!
Born with these tiny brains, and faced with the need to master a complex, unnatural world, humans have the longest childhood of the entire animal kingdom. They require so much care that both parents must be in attendance. This is the reason for another almost-uniquely human evolutionary trait: the ability of women to perform intercourse when they are not fertile. Most mammals can only copulate when the female is in estrus or "heat." Women do not have that limitation, and this is one way that men are encouraged to stay with their mates and share the childrearing duties.
I'm talking about way back in the Paleolithic Era, of course. Modern men are all responsible and caring, and would never dream of walking out on a wife and child to go looking for sex.
- 1. Enormous brains. The human forebrain, where we do all our conscious thinking, is qualitatively much larger than any other mammal's. It's the reason that we can invent tools, use complex language, do math, and even override instinctive behavior with reasoned and learned behavior; the result of all this is civilization.
In order for a newborn animal to survive, its brain has to be well-enough developed for the major neural circuits to minimally function. This is why in many baby animals, the head is disproportionately large.
But if a newborn human brain were as large as it should be, the head would not fit through the birth canal. To accommodate this as much as possible, the human birth canal is much wider than in the other ape species. - 2. However, this conflicts with the other evolutionary development: Bipedal walking. When we walk, we have to shift our weight to one side and then the other, to maintain balance while one foot is off the ground. Quadrupeds don't have this problem because they can keep three feet on the ground. The conflict comes from the fact that as the human birth canal has widened over hundreds of thousands of years, the pelvis has become broader, and the legs have moved farther apart.
This makes bipedal walking very difficult. When we lift one leg and transfer our entire body weight to the other leg, that is a very significant weight shift. And it has to be reversed and repeated over and over again, rapidly, while maintaining efficient forward motion!
Entire muscle systems have been re-routed to accommodate this. Most notable is our gluteus maximus, the pair of hemispheres that form the uniquely shaped human buttocks. No other ape has this, because their muscles are attached to their bones differently.
Therefore there is a limit to how large a newborn human brain can be. In fact human babies are arguably more helpless than any other mammal: Baby giraffes, for example, literally "hit the ground running" and scamper away.
But we need that brain to be just as large as possible, so the baby can breathe, suckle, swallow, and perform the minimum activities necessary for survival, and nonetheless require full-time care in order to simply survive.
This is why childbirth is so difficult for humans. It's a miracle that it works at all!
Born with these tiny brains, and faced with the need to master a complex, unnatural world, humans have the longest childhood of the entire animal kingdom. They require so much care that both parents must be in attendance. This is the reason for another almost-uniquely human evolutionary trait: the ability of women to perform intercourse when they are not fertile. Most mammals can only copulate when the female is in estrus or "heat." Women do not have that limitation, and this is one way that men are encouraged to stay with their mates and share the childrearing duties.
I'm talking about way back in the Paleolithic Era, of course. Modern men are all responsible and caring, and would never dream of walking out on a wife and child to go looking for sex.
