Humans have a uniquely long childhood, which sets us apart from all other species on the planet. We invest so heavily in our offspring that we have taken a different evolutionary path from even our closest primate relatives.


In her new book, Growing Up Human, anthropologist and archaeologist Dr Brenna Hassett explores every aspect of human development from conception to adulthood. Using her expertise, she studies the teeth and bones of our ancestors in the fossil record, in order to piece together the evolution of our strange and wonderful childhood.

Read on to find out why human childhood is weird.

It took two people to make you

We have a habit of pair bonding to produce kids, compared with other primates that have rather different family dynamics. For example, there are 700+ members of a mandrill ‘horde’, marmoset females have more than one male partner, and gorillas live in groups of females with a single male.

Only 15 per cent of our fellow primates opt for pair bonding like we do, and it is not seen in any of our closest relatives, the great apes.

Your existence is incredibly unlikely

Being conceived in the first place is pretty tough if you’re a human. Most primates have a much easier time getting pregnant than humans do – almost 90 per cent success rates compared to our 30 per cent.

Mother monkey carrying baby
Primates have fur, which allows their babies to cling on tightly © Getty Images

Your mum was not furry

Your mother had no fur for you to cling to. Most other primate babies are born clingers, except for the few that carry their tiny babies in their mouths, or hide them in trees.

Primate mums are lovely and furry, and primate babies have grasping hands that help facilitate this arrangement. Our own lack of fur might go some way to explaining the next utterly unlikely part of your childhood…

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You have a dad

The other parent. The one who carries stuff (no matter what gender!). Like other great apes, humans need help to raise their babies, but we tend to involve our pair-bonded mates more than other animals – only about 5 per cent of other mammal species get the dad involved in child rearing.

How much we get dads involved depends pretty heavily on our culture. There are dads of the Ba’Aka people, who live in Cameroon, Gabon and Central Africa, that carry their babies for 22 per cent of the day. American dads don’t quite average 50 minutes.

Grandma carrying baby
Humans continue to live for many years after they can no longer reproduce, which means granny can offer valuable help and experience in rearing grandchildren © Getty Images

You may have had a grandma

Human females stop being able to reproduce sometime around their fifth decade… but they keep on living. In contrast, elephants and chimpanzees, who live for almost as long as humans, will still be going through reproductive cycles throughout their whole lives.

The only other animals that have these utterly unlikely women around are whales – and as with humans, whale grandmas seem to be able to help their children and grandchildren thrive.

You ate like a zebra

The more watery an animal’s milk, the more likely it is to be doled out frequently to a baby who is running alongside the mother, like a zebra, or being carried, like a human.

If milk contains more concentrated nutrients like fat, then it is more likely that feeding happens only every so often, or for a limited time. For example, the milk of hooded seals is 60 per cent fat, and the mother will feed her baby for just four days.

Mother orangutan nursing her baby
Even though orangutans grow up comparatively faster than humans, they'll nurse for longer © Getty Images

You didn't breastfeed for long

Our closest relatives, the great apes, nurse their babies for far longer than we do. Mother orangutans will nurse for up to eight years, compared to the two-to-four-year average of humans globally.

But orangutans do not have a history of outsourcing milk like we do – we have thousands of years of archaeological evidence for baby bottles with animal milk residues, and 4,000-year-old cuneiform tablets with wet-nursing contracts from ancient Mesopotamia.

You were a child for a long time

We may stop nursing comparatively younger, but we take a long time to reach physical maturity. Even chimpanzees, our closest relatives, are grown up at 10 or 12. We don’t become fully developed and start having children of our own until much later.

Even deep in the past, it is thought that humans did not have children until they were around 20.

You are a serious investment

The rules of your society will determine how much investment to make in each child – and our species has chosen to bet heavily, for much longer than any other species.


For thousands of years children have been given the chance to learn for longer, whether it’s the boy lamenting his terrible schooldays in ancient Mesopotamia, or Aristophanes recalling the horrors of strict schoolmasters, or a Minoan girl learning to becoming a temple acolyte. But we still make decisions every day that allow some children the luxury of ever-longer dependence… and deny it to others. So the final shape of our childhood is, in the end, up to us.

Growing up human book cover


Brenna is a biological anthropologist based at University College London who researches the hidden histories of human lives using clues from bones and teeth. While her 'proper' research as an academic tends to involve intense laboratory work with very very small structures in teeth, her archaeological experience has taken her to a variety of interesting places. She's been menaced by goats while walking very straight lines on an island in Greece that is four hours from anywhere, she's had interesting amoebic conditions relating to the quantity of camel urine present in the sand around burials she was digging next to the Pyramids at Giza, and been attacked by fire ants in a banana grove in Thailand. She writes on the subjects that fascinate anyone interested in human beings: why we are how we are, how we got here, and whether large parts of human evolution were even a good idea in the first place.