Why does human birth always have so many complications? It seems as though it’s equally likely to hear about a complicated birth as it is to hear about a normal birth

Question

It seems like so often, and really more often than not, I hear about births having so many things go wrong with them. Why does it seem so hard for humans to hear have a normal birth with a healthy baby?

In: Biology

Answer 1

A lot of it has to do with the evolutionary tension between two of our biggest advantages — bipedalism and big brains.

Being bipedal requires narrower hips. Women have on average wider ones, which is why they have a “feminine” gait. But that leaves room for a smaller birth canal. That limits head size, which in turn limits brain size.

Humans have evolved a few ways to squeeze marginally more brain through a small birth canal. These include a women’s pubic symphasis (where the hip bones join in the front) actually stretching open a bit in birth, and of course babies having squishy heads.

But this push-pull between being a biped and the advantage of large brains means that historically women suffered mightily until modern medicine. Birth is incredibly dangerous for our species and it is estimated that around 1/4 of women who survived to adulthood died from complications from childbirth.