This is a comprehensive summary of “The Book of Humans” by Adam Rutherford. The book explores a brief history of culture, sex, war and the evolution of us.

what’s in it for me? discover why humans are – but also aren’t – special.#

Introduction

adam rutherford, the book of humans.

a brief history of culture, sex, war and the evolution of us.

narrated by morag sims and ariane stanley.

human beings are a special bunch.

our brains are capable of cognitive wonders.

our language is wildly complex.

it's no wonder that, to this day, we regard animals as mere beasts of the field.

but, in truth, human specialness is a marginal matter.

as these chapters reveal, the things we have in common with animals all but eclipse the things that differentiate us from them.

jam-packed with stories from across the animal kingdom, this whirlwind tour of evolutionary history may change the way you see yourself and your place in the world.

full of scientific discoveries, genetic breakthroughs and archaeological finds, these chapters are a delightful compendium of how animals evolve.

a quick warning before we dive in.

chapter 4 contains frank descriptions of animal sexuality.

animals use tools. but human tools are far more advanced.#

chapter 1 of 7 what makes you human?

is it the fact that you can call up a friend and communicate in a shared and highly complex language?

is it the fact that you can learn how to use, or even make, a computer?

or is it that you, unlike any other animal, can produce and discuss art?

we humans like to think of ourselves as kings among animals, but the same evolutionary processes that made us also made them.

animals have sex, just like us.

they build social structures, just like us.

they even use tools in some very human ways.

much as we hate to admit it, we humans simply aren't all that special.

and yet, at the same time, we are.

no other species has cognitive powers as sophisticated as ours.

no other has a language or culture as complex as ours.

there's a paradox at the heart of our existence.

we are simultaneously animals, and extraordinary among animals.

the key message here is, animals use tools, but human tools are far more advanced.

a tool is something external to an animal's body used to extend its power.

a tool can be a found object, a modified object, or something entirely manufactured.

in other words, a technology.

a barrette is a tool for clipping back hair.

a computer is a tool for conducting arithmetic operations.

for a long time, scientists believed that we were the only animals to use tools.

now we know that's not true.

chimpanzees, for example, use sticks to hunt termites.

orangutans use them to fish rivers.

and gorillas use them to test the depths of waters they need to ford.

yet despite an impressive range of tool use in the animal kingdom, the prevalence of tool use is low.

only 1% of all species use them.

technology, in other words, is relatively rare.

and no other animal's technologies are nearly as complex as ours.

that's partly because few other animals have brains as big as ours, but it's also because no other animal is as dexterous as we are.

you're not likely to see a dolphin crafting a violin, despite its densely packed neocortex.

flippers, alas, are not as nimble as fingers.

but, flippers notwithstanding, dolphins and their creative tool use do have a lot to teach us.

and that's what we'll explore in the next chapter.

very few animals acquire skills through both biological and cultural transmission.#

chapter 2 of 7.

if you're human, which i'm assuming 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 learn skill.

more specifically, it's something mothers teach their daughters.

this is a process scientists refer to as cultural transmission.

the key message here is, very few animals acquire skills through both biological and cultural transmission.

so far, the only non-human animals in which cultural transmission has been observed are dolphins, monkeys and birds.

let's look at an example.

in 2013, researchers in seattle, washington, conditioned a group of crows to recognise one face mask as threatening and another face mask as benign.

five years later, they approached the same birds, sometimes wearing one mask, sometimes the other.

the response was impressive.

the crows fled from the dangerous mask and ignored the neutral one.

apparently, they'd remembered.

but that's not the remarkable part.

what's fascinating is that the new birds in the group, that is, the offspring that had been born in the intervening years, responded the same way.

they seemed, in other words, to have learned from their elders how to assess the threat level of human faces.

like the dolphin mothers teaching their daughters how to sponge, or human caregivers teaching children how to speak, the crow parents have passed down the skill of face recognition socially, not genetically.

that's not to suggest that dna played no role at all.

too often, scientists talk about learned skills as though they were somehow separate from biology.

but cultural and biological evolution are fundamentally intertwined.

cultural transmission of ideas and skills requires a biological encoded ability to acquire them.

the human practice of farming, for example, is not biologically encoded, but the brains required to understand what will grow are, as are the hands required to cultivate the land.

agriculture laid the foundations for modern human society. but humans are not the world’s only farmers.#

chapter three of seven.

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 and civilisation could not have come into being had we not settled the land.

the key message here is agriculture laid the foundations for modern human society, but humans are not the world's only farmers.

the significance of farming in human evolution is difficult to overstate.

it's such a powerful force that it has even changed our genes.

the classic example is our ability to process milk, something we couldn't do for most of human history.

about 7,000 years ago, shortly after we began husbanding animals, something changed.

a mutation developed in our genetic code that gave us the ability to drink milk into adulthood.

think about that.

at the exact moment humans gained access to animal milk with all its fat and protein, we developed the ability to process it.

the practice of farming may be passed through cultural transmission, but the ability to consume the fruits of our farming is now written into our genetic code.

but we are not, it turns out, the only farmers.

in fact, we're relatively new to the game.

while humans have been farming for the last 12,000 years, leafcutter ants have been at it for 60 million.

you've probably seen them in documentaries, lugging around torn up bits of leaves.

contrary to popular belief, those leaves are not for eating.

instead, the ants feed them to a fungus they cultivate in their nests, one that's necessary for their survival.

as sophisticated as this technique may be, the ants are still only farming a single fungus, a far cry from the astounding variety of crops that humans farm.

here, again, we see the tension at the heart of human existence.

we are just another animal.

and yet, at the same time, we're so much more.

in the next chapter, we'll see how that paradox plays out in a very different realm of animal life.

humans have decoupled sex from reproduction, and we aren’t the only ones.#

chapter 4 of 7 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.

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.

the key message here is humans have decoupled sex from reproduction.

and we aren't the only ones.

sex, of course, is necessary to ensure the survival of our species.

but, according to one estimate, only one in every thousand sex acts that could result in a baby actually does.

and that's only counting heterosexual acts of vaginal penetration.

if we included all the other sex acts, from anal sex to rope play to cunnilingus, the ratio would be even more skewed.

sex may be a biological imperative, but our interest in it has clearly evolved way beyond that.

in that regard, we aren't alone.

pretty much all the birds and bees are doing it, well beyond their need to reproduce.

oral sex, for example, is nearly ubiquitous in nature.

ditto masturbation.

homosexuality abounds across the animal kingdom, from elephants to lions, giraffes to bats.

and female bonobos rub their genitals together nearly every two hours.

we still can't fully explain these non-procreative sex acts, though fun seems like a pretty plausible explanation.

but according to the author, scientists are reluctant to embrace that hypothesis.

pleasure cannot be scientifically measured, and we can't ask non-human animals if they're enjoying all that sex.

the idea that animals engage in certain behaviours because, well, they just feel good is a hard one for most scientists to embrace.

instead, they focus on potential evolutionary purposes of non-reproductive sex acts.

in humans, the obvious example would be sex as a form of social bonding.

but with only a few exceptions, the vast majority of sex acts in the animal world do not serve a clear evolutionary purpose.

scientists, argues the author, might just need to open themselves up to the possibility that these acts are driven largely by the pursuit of pleasure.

the primary driver of biological evolution is dna.#

chapter 5 of 7 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 key message here is, the primary driver of biological evolution is dna.

dna is a molecule that acts like a kind of biological instruction manual, telling organisms how to develop, function, grow and reproduce.

it does that through genes, sequences of dna that encode physical traits.

if the traits enhance an organism's ability to survive, the dna underwriting them will be selected by nature and passed down to the next generation.

if, by contrast, the traits impair the survival of the organism, they will be slowly weeded out.

many of our genes are shared with all living organisms on earth.

these genes are billions of years old and tend to encode very basic bits of biochemistry.

a smaller number of genes are shared by us and all other animals.

an even smaller number are shared by us and all the mammals.

and a smaller number still are shared by us and the other great apes.

over time, dna undergoes subtle changes by way of random mutations.

you can think of these as the genetic equivalent of a typo, a spelling error that slips through the cracks as a result of bad copy editing by the proteins responsible for the job.

it's through these mutations that our genes change and different species evolve.

thanks to radical advances in genome sequencing, we've made significant progress in understanding how early humans evolved into the beings we are today.

we now know, for example, that a very short bit of dna is responsible for dexterity in our hands, without which we could never have begun to craft sophisticated tools.

we know when our toes became shorter, allowing us to become bipedal.

and we know when our bodies attained the anatomical ability to acquire language.

in short, we know a lot about how humans became distinctly human.

and we learned it all by studying that extraordinary molecule that encodes all life on earth, dna.

human speech and language set us apart from other animals.#

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.

the key message here is, human speech and language set us apart from other animals.

we are not, of course, the only animals to vocalise.

dogs bark, cats meow, plenty of animals communicate vocally.

there are even some that, like humans, have the ability to acquire language by copying the sounds made by other members of the species.

some birds, for example.

but the birds with that ability have just a handful of songs.

humans, by contrast, speak over 6,000 distinct and constantly evolving languages.

our brains are the only brains in the animal world capable of language acquisition, with the only animals to use complex syntax and grammar and the only ones with tens of thousands of words at our disposal.

these words are essentially symbols.

when you see an ear, you know you're looking at an ear, because, through experience, you know what an ear looks like.

when you read the word ear, you're not looking at an ear itself, but you know what the word refers to.

that's because you have the ability to understand symbolic units of meaning.

again, you aren't the only animal with that ability.

prairie dogs, for example, use different alarm calls for different predators.

like human language, these calls are a form of vocal symbolism predicated on the ability to equate one thing with another.

in this case, a specific call with a specific predator.

but compared to human communication, these alarm calls are primitive.

for now, language is unique to us.

it's also the essential prerequisite to behavioural modernity, the thing that allowed us to become the people we are today.

behavioral modernity in humans is marked by imagination, abstract thinking, and the ability to make art.#

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 cafe.

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.

the key message here is behavioural modernity in humans is marked by imagination, abstract thinking, and the ability to make art.

homo sapiens reached full behavioural modernity about 40,000 years ago.

that's the moment we became the humans we are today.

it's the moment we started carving figurines, and the moment we started painting cave walls.

it's the moment we started crafting decorative jewellery, and the moment we began sculpting fantastical creatures out of ivory and wood.

from borneo to france, the world today is replete with art and artefacts dating back to this period, even primitive flutes carved from the bones of swans.

one of the most famous of these artefacts is the louvenmensch, or lion man, a chimera carved from the ivory tusk of a woolly mammoth.

it is an extraordinary work of art, reflecting not only finger dexterity and fine motor control, but foresight in selecting the right bone and making a plan to carve the figure.

it suggests an understanding of nature and, above all, an ability to imagine a thing that does not exist, a make-believe creature with the body of a human and the head of a cave lion.

it is, in short, the product of a sophisticated mind.

but the louvenmensch is not the oldest example of figurative art.

in 2018, scientists dated a series of cave paintings in northern spain at 64,000 years old, to a period when the only people on the continent of europe were not homo sapiens.

what does that mean?

it means our human cousins, homo neanderthalensis, were making art some 20,000 years before we invaded their territory.

even some of the abilities we see as uniquely ours turn out to be shared by another species.

final summary#

Conclusion

the key message in these chapters is this.

hamlet famously called us the paragon of animals, an apt description for the species homo sapiens.

we share the same basic biological blueprint as all other species, and we became who we are through the same evolutionary forces.

and yet in the sophistication of our language and the complexity of our culture, we are unlike any other, both decidedly animal and decidedly unique.

here's something else to get that sophisticated mind of yours thinking.

consider your connectedness.

next time you find yourself feeling alienated or alone, remember that you are connected to every other creature on earth, through genes, through evolution, through social practices and sexual activities.

you can never be fully disconnected from the great wide world of creatures, and because you're human, you have the cognitive ability and emotional capacity to reflect on that truth.

have you got any feedback for us?

we'd love to hear what you think about our chapters.

just drop an email to remember at summarybook.org with the book of humans as the subject line and share your thoughts.

Discover more book summaries in the same category or by the same author.

The Mosquito

Nature & the Environment45 min read