Our evolutionary path to parenting—and sharing the load

The following is an excerpt from “The Creatures’ Guide to Caring: How Animal Parents Teach Us That Humans Were Born to Care” by Elizabeth Preston.

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The Creatures' Guide to Caring:
How Animal Parents Teach Us That Humans Were Born to Care

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In the spring of 2007, scientists who were using a robotic submarine to explore the deep sea off the California coast spotted a lone purple octopus. They recognized this octopus from her distinctive scars, having seen her just the previous month. Today, she was resting on a nearly vertical rock face, her body curled over more than 150 eggs.

This gave the scientists a rare opportunity to study parental care in a deep-sea octopus species. In general, octopuses and other cephalopods live for only a year, maybe two. After the females mate and lay eggs, they commit themselves entirely to protecting their brood. Coastal octopuses may tuck their eggs into a rocky den; mothers who live in the open ocean simply make a den out of their arms.

The mother stops eating. She cleans the eggs, shoots jets of water across them, and fends off other animals. She wastes away as the eggs grow. As soon as the baby octopuses hatch, the mother dies.

So the team observing the octopus near California knew they were about to witness her death. Over the following months, they periodically sent their submersible back to check on her.

As they expected, she didn’t seem to be eating anything or budging from her post. Her violet skin paled and slackened; her eyes clouded. She became a nearly white ghost haunting the rock face. And the baby octopuses in their egg cases were a little larger each time scientists checked. Their eyes slowly grew visible, two dark dots peering out from inside each translucent egg case. Finally, the submersible returned one day to find the eggs empty and all of the octopuses, including the mother, gone.

It was nearly four and a half years after she had laid her brood.

The feat was unprecedented among octopuses. In shallow water, where scientists have had more chances to spy on them, octopus mothers tend their eggs for a few months or less.

It was also unprecedented among animals generally. The longest typical egg incubations, which are among kiwis and some albatross species, last about 11 weeks. Elephant pregnancies last up to 22 months (and I thought I was ready for a cocktail). There are salamanders who carry their developing young inside their bodies for three years or more. They can eat meals, though.

Scientists speculated that a slow metabolism and the frigidity of the water may have combined to keep the octopus mother alive. Unfed, she waited 53 months—230 long weeks in the dark—until her work was done.

It’s tempting to imagine her as a martyr, a paragon of motherly love. But behind every astonishing act of parental care, as well as every clutch of eggs that’s simply tucked under a leaf and left, is cold math.

Random accidents during cell division create errors in our DNA with a certain frequency. Those mistakes in writing the instructions for life are most often neutral or problematic. But a tiny fraction of the errors cause a mutation that gives an animal an edge in staying alive and reproducing, and can be passed to the next generation.

Depending on countless factors—competition between neighbors, scarcity of mates, predators, luck, the weather—some of those helpful mutations will persist and become more and more common in future generations, evolving into a defining trait of a species. Congratulations! Now you have tusks, say, or a dazzling song.

Researchers can deduce how caretaking evolved by studying animals who care for their young alongside those who don’t. They can also look at species that are closely related to each other but have different parenting styles, or animals that are as flexible in their methods as a human who subscribes to a new parenting podcast each week. In this way, scientists are revealing the forgotten evolutionary math—like faint equations on an erased chalkboard—that brought all of Earth’s animals to where they are today.

It’s not just a question of which creatures put their energy into raising children to adulthood, or literally kill themselves just to get their eggs hatched, or do no caretaking at all. In some branches of life, the invention of parental care was the first falling domino in a cascade of events that changed the world.

Let me tell you about a wasp.

The social life of a paper wasp passes through dramatically different phases. Each female starts her life as part of a bustling hive. The individuals work together in a collective. But after a female mates, she leaves her and sets off on her own.

The solo insect builds a small nest and lays a few eggs. When those eggs hatch into daughters, she dedicates herself to feeding and caring for them. It’s a strenuous life phase that often kills the mother. If she survives, though, her daughters grow up to become her companions and helpers: a tiny community.

The mother lays more eggs, but now the daughters tend them, and the family grows and grows. It becomes a whole new cooperative hive.

The complex, highly organized colonies of wasps, bees, and ants have made these insects some of the most successful species on Earth. They’re resilient and widespread because every worker does her part to keep the whole community humming, like the components of a machine.

Or like the members of a human society.

Life as a Homo sapiens, not unlike life as a wasp, means relying on coordination with others. That’s true whether you’re part of a small community of foragers in Namibia or a high-rise apartment building in Chicago. We play different roles; we’re not self-sufficient. And the story of how we came to live in these buzzing societies, like the story of the paper wasps, starts with a single parent and child.

In our distant mammalian past, furry mothers fed and cared for their babies alone. Then, at some point in our evolution from ancient ape into modern human, our children probably began staying home to help out after they grew up, like the wasp daughters. The mothers’ mates stuck around, too, and discovered the benefits of fatherhood. Gradually, those families grew into communities.

Ancient humans didn’t simply live near each other and share a fire pit. They pitched in—siblings, dads, grandmothers, neighbors—to jointly care for kids. This shared childcare may have given our species a boost so that we could become the big-brained, brilliant, planet-dominating apes we are today.

Some authors have argued that other factors were the key to making us human. Language, for example. Or learning to make fires and cook our food.

But we wouldn’t have needed language with no one around to talk to. We wouldn’t have had big pieces of meat to char over a flame without other upright primates to help us hunt it (or stand around commenting on our grilling technique). Being together with others is a critical piece of the human story. And what brought us together, ultimately helping to birth human society as we know it, may have been the need to raise our kids.

Today, it can be hard to encounter other members of our species in rush-hour traffic or an internet comments section and imagine that humanity was built on cooperation. Yet this is the message hinted at by the animal caretakers who populate the world, and hidden within our own cells and skulls: Humans are born to care.

From THE CREATURES’ GUIDE TO CARING by ELIZABETH PRESTON, published by Viking, an imprint of Penguin Publishing Group, a division of Penguin Random House, LLC. Copyright © 2026 by Elizabeth Preston