Quora .

This question originally appeared on Quora. Answer by C Stuart Hardwick, SciFi Author.

Because of this:

Screen Shot 2016-08-18 at 6
Humans difficult births may result from an evolutionary snag. Photo courtesy of author.

Our little branch of the primate family tree has been evolving rapidly for millions of years, during which we reacted to wild climate swings, competition with African apex predators and other pressures by growing smarter, sweatier, more dextrous, and exclusively bipedal. We suffer from bad backs and fallen arches (among other things) because this is a lot of change over a short evolutionary time frame, and we haven’t had time to fully adapt to our “new” (hunter-gathering) niche.

But that’s nothing. Starting about two million years ago, we dumped fertilizer on our brains. Actually, we started using our already large brains to make tools, hunt more effectively using teamwork, and generally make better use of our environment. Early in this period, we also started using fire and lost most of the strength in our jaws. Together, these changes, combined with continued climate swings, created a feedback loop that caused our brains to sprout like pumpkin seeds in a hot house.

We REALLY have not had time to fully flesh out this change. Our long period of infantile dependency is a trade-off between the desirable survival trait of getting young quickly ready to live on their own and having babies so large their mothers can’t survive thier birth. An adult brain consumes a quarter of a person’s energy, a baby with anything close to a mature brain would put its mother at serious risk of starvation. As it is, large babies can overload a mother’s organs and jam tight in the birth canal. Human hips just sometimes aren’t wide enough to accommodate the giant noggin.

And we may have it lucky. There is evidence that suggests some australopithecines may have had to corkscrew their babies into the world just to get their babies skull to squeeze through their narrower hips. The wide hips young men the world over like to pretend they aren’t admiring at the beach are a powerful survival trait for pre-industrial humans.

So it shouldn’t be surprising that humans have trouble giving birth. Even accounting for increases in body size, we are total freaks:

The only other animal with brains close to as large as ours given body weight are dolphins, and they use much of their prodigious grey matter for echolocation.

At least until we invented antibiotics, surgery, and Lamaze classes, we were still in the process of catching up to our giant brains by evolving wider hips, more robust reproductive organs, and (very likely) higher neuron density. Now that we have hospitals and over-priced health care, our fate, God help us, is in our own hands.

More from Quora: