Why Is Childbirth So Painful? (Actually, It Could Be Worse)

This article is an excerpt from the Shortform summary of "Sapiens: A Brief History of Humankind" by Yuval Noah Harari. Shortform has the world's best summaries of books you should be reading.

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Why is childbirth so painful? What happened in the evolution of humans to make it as arduous as it is?

Childbirth is painful because of our relatively narrow hips and the relatively large brains of infants. Although we’re not sure why humans evolved such large brains, we do know that narrow hips had some evolutionary advantages.

We’ll cover how humans evolved the bodies they did and why childbirth is so painful.

Why Is Childbirth So Painful?

Before we can answer, Why is childbirth so painful? we need to look at the anatomical evolution of humans. Early humans had two characteristics that contribute to understanding why childbirth is so painful.

Characteristic #1: Large Brains

Mammals that are 130 lbs typically have a brain that’s an average of 12 cubic inches. In contrast, the brains of early humans were 36 cubic inches. Today, our average brain size is 73-85 cubic inches, and the brains of Neanderthals were even bigger than ours.

It seems like large brains would give us and our fellow humans an obvious advantage over other animals, but it wasn’t necessarily an asset to early humans.

Big brains take a lot of energy to fuel. Our brains make up 2-3% of our body weight, but use 25% of our energy. (The brains of our ape siblings only use 8% of their energy.) When you’re in the middle of the food chain, trying to catch small animals and keep out of the way of big ones, using your energy to power your brain instead of your muscles isn’t the smartest strategy.

We still don’t really know why we evolved such large brains when there was little use for them in early history. It was a bad use of our energy.

As we’ll see, the fact that humans have big brains, and therefore big brains, is a factor in the answer to Why is childbirth so painful?

Characteristic #2: Walking Upright

Another seemingly unlikely characteristic that leads to painful childbirth is the fact that humans evolved to walk upright.

Like having a big brain, walking upright seems like an unequivocally positive trait to us today, in part because we still walk upright and can’t imagine moving any other way. There were both advantages and disadvantages to walking upright.


  • A better view: When you’re standing, it’s easier to see the lion hiding in the grass or the prey oblivious to you.
  • The ability to use tools: When you don’t need your arms for moving around, they’re freed up for other tasks, like signaling to others and using tools. As we evolved more nerve endings and agile muscles in our hands, our tools became more sophisticated.


  • An unstable skeleton: Because we’re built to walk on all fours like most mammals, our skeletal structure doesn’t easily support our large heads. Consequently, we get back and neck aches.
  • Narrow hips: To walk upright, women (and men) evolved narrower hips, but this was bad news for childbirth. As women’s hips were getting narrower, babies’ heads were getting bigger.

Why Childbirth Is So Painful

Narrow hips especially had far-reaching consequences for humans, creating a domino effect that led to helpless babies. This was because the women who survived the dangerous activity of childbirth (and continued to pass on their genes through subsequent births) were the ones who gave birth early in the fetus’s gestation, when the baby’s head was smaller and undeveloped. Women actually evolved to have babies prematurely so childbirth wouldn’t be so painful.

Consequently, women evolved to give birth earlier when the fetus is less developed. This means that human infants are undeveloped and helpless compared with other animal infants. For instance, a colt can start to run soon after birth, and a kitten finds food on its own after a few weeks. But human children are dependent on their parents for years.

The fact that human children were vulnerable for years after birth meant that human adults had to care for and protect them for years. Like having a big brain, this wasn’t an obvious advantage for early humans. They needed their energy for activities like escaping the jaws of larger, stronger animals.

The Consequences of Having Premature Babies

Despite the risks involved in caring for vulnerable infants, their existence created unique social situations for humans. These situations and the resulting societal bonds may have contributed to the rise of human dominance in the animal kingdom. Because children were so helpless, mothers relied on family members and neighbors to raise them. This formed social bonds and the potential for socialization.

Why is childbirth so painful? Essentially, babies have big heads and mothers have narrow hips. But if human gestation were longer, it could be a lot worse.

Why Is Childbirth So Painful? (Actually, It Could Be Worse)

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Amanda Penn

Amanda Penn is a writer and reading specialist. She’s published dozens of articles and book reviews spanning a wide range of topics, including health, relationships, psychology, science, and much more. Amanda was a Fulbright Scholar and has taught in schools in the US and South Africa. Amanda received her Master's Degree in Education from the University of Pennsylvania.

One thought on “Why Is Childbirth So Painful? (Actually, It Could Be Worse)

  • April 27, 2020 at 3:52 am

    It could be a great book to read. I will recommend this article to my friend, who is undergoing Bradley Method and BirthForMen birth classes. I hope he will be able to share this article and book to others and may relate things to childbirth. I also hope that more people can find this site and can help them. Cheers!


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