The Book of Humans summary

If you’re human, which you probably are, you’ve used tools your whole life. You’ve used a pencil to write something down. You’ve used a glass to drink water. But have you ever used another animal as a tool? This is common practice among the bottlenose dolphins of Shark Bay, Australia. These creative tool users nestle their beaks into living sea sponges before foraging the craggy sea floor. The sponge acts as a sort of nose cap, protecting the dolphins’ beaks from all the scratchy nooks and crannies where they go looking for food – one creature using a second to eat a third.

But what these dolphins do with the sponge is only half the story. Just as important is how they learn to do it. Sponging isn’t encoded in dolphin DNA; it’s a learned skill. More specifically, it’s something mothers teach their daughters. This is a process scientists refer to as cultural transmission.

Unless you’ve been living under a rock, you’ve probably heard of the paleo diet, which encourages eating the way our ancestors did – or at least the way some people think they did.

Proponents of paleo claim – not uncontroversially – that agriculture was a disaster for the human digestive system. They aren’t the only ones critical of farming. Many scholars have argued that the transition to agriculture sparked the gradual demise of egalitarian social structures. On the other hand, modern society as we know it wouldn’t exist without agriculture. Books, museums, Spotify, video games – basically, everything you might love about life in civilization could not have come into being had we not settled the land.

We do it in bed or on tables, alone or in groups. We do it on beaches or against trees, in the morning or late at night. Sometimes we do it with people we love. And sometimes, we do it with people we hate.

Yup, you guessed it: it’s sex, an activity for which humans show remarkable enthusiasm. From masturbating to copulating, we do it all, and we do it with gusto. In fact, just about the only thing we don’t do when it comes to sex is have it for the sole purpose of making babies.

Same same, but different. Different in degree, not in kind. However you want to put it, by now it should be clear: there’s much we share in common with other animals and just as much that sets us apart. Ask any self-respecting high schooler why that is, and you’ll probably get a clear answer. We’re similar because we evolved from the same early organisms. We’re different because we evolved along different tracks. 

But what does that mean exactly? How did that work?

The process that enables you to understand these words is extremely complex. The mere fact that one human is able to string together words in such a way that you can understand them is a stunning feat, one unique to Homo sapiens.

At the heart of this act is a complex anatomical and neurological architecture. Without it, no human could generate the vast array of sounds necessary for human language. This architecture includes a highly innervated and versatile tongue, which descends past an intricately carved hyoid bone into a powerful larynx. The larynx, in turn, is connected to a nose, which is linked to the many other muscles of the face. And this entire apparatus can be manipulated at will, due to an extremely high degree of motor control. There’s no other animal on Earth with as sophisticated a biological basis for language.

Physically speaking, there’s not much difference between you and a human being living on the African continent 200,000 years ago. Give them a haircut, hand them a trendy outfit, and they’d fit right in at your local café. Like you, they’d even have the anatomical ability to speak. What they wouldn’t have is language – not yet, anyway.

It took some time for language to develop after humans gained the biological ability to speak. About 130,000 years. What changed during that period wasn’t our DNA, but our culture. And it didn’t stop with language. Over time, our grasp of symbolism expanded even further, from the ability to understand words to the ability to create art.