The Book of Humans Read online

  THE

  BOOK OF

  HUMANS

  THE STORY OF HOW WE BECAME US

  ADAM RUTHERFORD

  CONTENTS

  Title Page

  List of Illustrations

  Introduction

  PART ONE

  Humans and Other Animals

  TOOLS

  What it Takes to Be a Maker

  Tooled-up Animals

  Sponging Dolphins

  The Birds

  Fiery the Angels Fell

  War for the Planet of the Apes

  Farming and Fashion

  SEX

  The Birds and the Bees

  Autoeroticism

  Mouthing Off

  Whole Lotta Love

  Homosexuality

  And Death Shall Have No Dominion

  Sex and Violence

  PART TWO

  The Paragon of Animals

  Everyone is Special

  Genes, Bones and Minds

  24 – 2 = 23

  Hands and Feet

  Trippingly on the Tongue

  Speak Now

  Symbolism in Words

  Symbolism Beyond Words

  If Only You Could See What I’ve Seen with Your Eyes

  Know Thyself

  Je Ne Regrette Rien

  Teach a Village to Fish . . .

  The Paragon of Animals

  Also by Adam Rutherford

  Acknowledgements

  References

  Copyright

  ILLUSTRATIONS

  By Alice Roberts

  The Venus of Hohle Fels

  An Oldowan chopper

  A sponging dolphin

  A firehawk

  The fashionable Julie

  The giraffe’s recurrent laryngeal nerve

  A most intricate hyoid

  The Lion Man of Hohlenstein-Stadel

  A Javanese fish hook

  INTRODUCTION

  ‘What a piece of work is a man!’ marvels Hamlet, in awe at our specialness.

  How noble in reason! How infinite in faculty!

  In form, in moving, how express and admirable! In action how like an angel!

  In apprehension how like a god! The beauty of the world! The paragon of animals!

  ‘The paragon of animals’ is a lovely phrase. Hamlet exalts us as truly special, touching the divine, limitless in our thought. It’s a prescient phrase too, as he raises us above other animals while acknowledging that we are one. Just over 250 years after William Shakespeare wrote those words, Charles Darwin irrefutably cemented humankind’s classification as an animal – the slightest of twigs on a single, bewildering family tree that encompasses four billion years, a lot of twists and turns, and a billion species. All of those organisms – including us – are rooted in a single origin, with a common code that underwrites our existence. The molecules of life are universally shared, the mechanisms by which we got here the same: genes, DNA, proteins, metabolism, natural selection, evolution.

  Hamlet then ponders the paradox at the heart of humankind:

  What is this quintessence of dust?

  We are special, but we are also merely matter. We are animals, yet we behave like gods. Darwin sounds a bit like Hamlet, declaring that we have ‘god-like intellect’, yet we cannot deny that man – and, to bring his language into the twenty-first century, woman – carries the ‘indelible stamp of his lowly origin’.

  This idea, that humans are special animals, is at the root of who we are. What are the faculties and actions that put us on a pedestal above our evolutionary cousins? What makes us animals, and what makes us their paragon? All organisms are necessarily unique, so that they can exist within and exploit their own unique environment. We certainly think of ourselves as pretty exceptional, but are we really more special than other animals?

  Alongside Hamlet and Darwin comes a possible challenge to our ideas of human exceptionalism, from an arguably lesser piece of modern culture, the animated superhero film The Incredibles: ‘Everyone is special . . . which is another way of saying that no one is.’

  Humans are animals. Our DNA is no different from anything that has lived in the last 4,000 million years. The coding system employed within that DNA is no different either: the genetic code is universal as far as we know. The four coded letters that make up DNA (known as A, C, T and G) are the same in bacteria and bonobos, orchids, oaks, bedbugs, barnacles, triceratops, Tyrannosaurus rex, eagles, egrets, yeast, slime moulds and ceps. The way they are arranged in those organisms, and how they are translated into the protein molecules that enact the functions of a living being are all fundamentally the same too. The fact that life is organised into discrete cells is also universal,1 and these incalculably numerous cells harvest energy from the rest of the universe in a process common to all of them.

  These principles are three of the four pillars of biology: universal genetics, cell theory, and chemiosmosis, which is a rather technical yet elegant word for the basic process of cellular metabolism – how cells draw energy from their surroundings, to be spent in the process of living. The fourth pillar is evolution by natural selection. Combined, these grand unifying theories coalesce to reveal something unarguable – that all life on Earth is related by common ancestry, and that includes us.

  Evolution is slow, and the Earth has been host to life for the vast majority of our planet’s existence. The timescales we talk about so casually in science are utterly baffling to comprehend. Even though we are a latecomer to life on Earth, our species is more than 3,000 centuries old. We have traversed that ocean of time largely unchanged. Physically, our bodies are not drastically different from Homo sapiens in Africa 200,000 years ago.2 We were physically capable of speaking then as we do today, and our brains were not significantly different in size. Our genes have responded in small part to changes in the environment and diets as we migrated within and out of Africa, and genetic variants account for the minuscule percentage of DNA that spells out the differences between individuals, changes in the most superficial characteristics – skin colour, hair texture and a few others. But if you tidied up a Homo sapiens woman or man from 200,000 years ago, gave them a haircut and dressed them in twenty-first-century clothes, they would not look out of place in any city in the world today.

  There’s a conundrum in that stasis. Though we may not look different, humans did change, and profoundly. There’s debate about when this transition occurred, but by 45,000 years ago, something had happened. Many scientists think that it was a sudden change – sudden in evolutionary terms means hundreds of generations and dozens of centuries, rather than a thunderbolt. We don’t quite have the language to relate to the timescales involved in such transitions. But what we can observe from the archaeological record is that we see the emergence and accumulation of a number of behaviours that are associated with modern humans, and there was a time before that where we see fewer or none of them. Given how long life has existed on Earth, this switch happened relatively in a heartbeat.

  The transformation occurred not in our bodies or physiology or even in our DNA. What changed was culture. In scientific terms, culture refers broadly to the artefacts that are associated with a particular time and place. They include things like tools, blade technology, fishing gear, and use of pigment for decorative purposes or jewellery. The archaeological remains of a hearth show the ability to control fire, to cook, and maybe its position as a social hub. From material culture, we can infer behaviour. From fossils we can try to piece together what people looked like, but with archaeological evidence of the paraphernalia of our ancestors’ lives, we can address what people were like in prehistory, and when they became like that.

  By 40,000 years ago, we were designing decorative jewelle
ry and musical instruments. Symbolism in our art was rife, and we were inventing new weapons and hunting technology. Within a few millennia, we had fostered dogs into our lives – tamed wolves that accompanied our search for food long before they became our pets.

  The concatenation of these behaviours is sometimes referred to as the Great Leap Forward, as we jumped into a state of intellectual sophistication that we see in ourselves today. Alternatively, it’s a ‘cognitive revolution’, but I dislike the use of that phrase to describe a process which was both continuous and probably lasted a few thousand years or more – real revolutions should be thunderbolts. Nevertheless, modern behaviour emerges permanently and quickly in several locations around the world. We began to carve complex figurines, both realistic and abstract, sculpted make-believe chimeras out of ivory, and we adorned cave walls with pictures of hunts, and of animals important to our lives. The earliest piece of figurative art by Homo sapiens that we know of is a 40,000-year-old twelve-inch statue of a lean man with the head of a lion. It was carved from a mammoth tusk during the last Ice Age.

  Soon after that time we were making small statues of women. They are known today as Venus figurines. We don’t know if there was a specific purpose to these dolls, though some researchers think they may have been fertility amulets, as their sexual anatomy is exaggerated: bosomy women with swollen labia, and often bizarrely small heads. Maybe they were just art for art’s sake, or toys. Either way, to create such sculptures requires great skill and foresight, and a capacity for abstract thought. A lion-man is an imagined being. The Venus amulets are deliberate misrepresentations, abstractions of human bodies. These figures cannot exist in isolation either: artisan craft requires practice, and though today only a handful of these beautiful works of art remain, they must represent an iterative process, a lineage of skilled craftspeople.

  Some of these types of traits pop up before the full transition to our modern behaviour, but they do so fleetingly, and then vanish from the archaeological record. Homo sapiens were not the only humans to have existed in the last 200,000 years, and not the only ones to have refined culture. Homo neanderthalensis, far from the brutes of popular lore, were simply people too. We are wrong to think of them as merely upright apes, living in dust with crude language and tools, all set for extinction. Neanderthals showed clear signs of modern behaviour: they made jewellery, employed complex hunting techniques, used tools, had a control of fire, and made abstract art. We have to consider that they also were sophisticated in a way indistinguishable from our direct Homo sapiens ancestors, which undermines the uniqueness of our own forward leap. Though we have traditionally considered Neanderthals to be cousins to us, they were also ancestors: we now know that our lineage and theirs diverged more than half a million years ago, and both groups were isolated in time and space for almost all of that period. But our ancestors left Africa some 80,000 years ago, and were immigrants into Neanderthal territory. We reached Europe and central Asia, and around 50,000 years ago, we bred with them. Their bodies were different enough that they lie outside the range of human physical diversity as we see it today – a bit less chin, a bit more chest, heavy-set brows and robust faces. They weren’t so different that we didn’t have sex with them, women and men from both sides of the species fence, and together we had children. We know this because our genes are in their bones, and theirs are in our living cells. Most Europeans carry a small but significant percentage of DNA that was acquired from Neanderthals, and this blurs any hope of a clear boundary between two sets of people that we have declared separate species – that is, organisms that cannot produce fertile offspring. Though Neanderthal DNA is slowly being purged from our genomes for reasons that are not fully understood, humans today bear their living genetic heritage, as we do the genes of another type of human, the Denisovans, further to the east, and maybe others that are yet to be discovered but whose legacy sits within our DNA.

  The Venus of Hohle Fels

  When we first met, the Neanderthals and those other people were not long for this world, and by around 40,000 years ago, Homo sapiens had outlived the last of them. Whether the Neanderthals had undergone a full transition to the behavioural modernity as we saw in Homo sapiens, we do not know, and may never know, but the evidence is pointing towards those cavemen and women being much like ourselves in every way.

  We lived and they died. We don’t know what gave Homo sapiens the edge over Neanderthals. All life is set for extinction over a long enough timescale: more than 97 per cent of species that have ever existed are already gone. The Neanderthals’ tenure on Earth was much longer than we have racked up so far, and we are yet to firmly understand why their light was finally snuffed out 40,000 years ago. We don’t think there were ever very many Neanderthals, which may have contributed to their demise. Maybe we outsmarted them. Maybe we brought with us diseases that we had lived with and earnt immunity to, but which were lethal to a virgin population. Maybe they simply petered out of existence. What we do know though is that around this time, the last type of human began to permanently and globally show signs of who we are today.

  We certainly outbred all our nearest relatives. Homo sapiens went forth and multiplied very effectively. We’re the dominant life form on Earth by many measures, if ranking matters to you (though bacteria outnumber us – you carry more bacterial cells than human ones – and are far more successful in terms of longevity. They have a four-billion-year lead on us, and no prospect of extinction). Today there are upwards of seven billion humans alive, more than at any time in history, and that number is still rising. Through our ingenuity, science and culture, we have eradicated many diseases, drastically reduced infant mortality, and extended lifespan by decades.

  Hamlet marvels at our brilliance, as have scientists, philosophers and religions for millennia. But the progress of knowledge has chipped away at our specialness. Nicolaus Copernicus dragged us away from a world at the centre of the universe to one merely orbiting an ordinary star. Twentieth-century astrophysics revealed our solar system as an average one among billions in our galaxy, which itself is one of billions in the universe. We still only know of one world that harbours life, but since 1997 when the first planets beyond our Sun’s gravity were discovered, we have learnt of thousands in the heavenly firmament, and in April 2018 a new satellite was launched specifically to seek out strange new worlds. We’re getting a good grip on the conditions required for chemistry to transition into biology, and for life to emerge from a sterile rock. The question of whether there is life beyond Earth has mutated: it would now be surprising if there weren’t living things elsewhere in the universe. That is all still to come, and for now, we only know of life on Earth. But we might not be as unique as we once thought, and the more we learn the clearer that becomes.

  On Earth, Charles Darwin began the process of inching us back into the natural world, and away from special creation. He showed that we are animals, evolved from other animals, and placed us firmly as a creature begotten not created. All of the incontrovertible molecular evidence of those pillars of biology was yet to come when he exposed the world to his big idea in 1859 in On the Origin of Species. He avoided including humans in that great work, but teased us that his mechanism of natural selection would soon shed light upon our own origins. In The Descent of Man in 1871, he applied his meticulous and foresightful brain to our genesis, and cast us as an animal evolved just like every organism in Earth’s history. Mostly bald, you’re an ape, descended from apes, your features and actions carved or winnowed by natural selection.

  In that sense we are not special. We evolved with a biology indistinct from all life, and under the auspices of a mechanism that is similarly universal. But evolution also equipped us with a suite of cognitive powers that gave us, ironically, a sense of separateness from nature, because it allowed us to develop and refine our culture to a level of complexity well beyond any other species. It gave us a clear sense that we are special, and specially created.

  Yet many of the
things once thought to be uniquely human are not. We have extended our reach so far beyond our grasp by utilising nature and inventing technology. But many animals also use tools. We have decoupled sex from reproduction, and almost always have sex for fun. Scientists are reluctant to admit the possibility of pleasure in animals, but even so, a huge proportion of sexual activity in animals does not and cannot result in reproduction. We are frequently a homosexual species. Once – and in many places to this day – homosexuality was decried as contra naturam, a crime against nature. In fact, sexual acts between members of the same sex abound in nature, in thousands of animals, and, for example, may well dominate male giraffe sexual encounters.

  Our ability to communicate appears to trump all other animals, though maybe we just don’t know what they’re saying yet. I am writing this book and you are reading it, which is a degree of communication that has evolved far beyond any other level we have observed in any other species. Though that certainly makes us different, a mantis shrimp doesn’t give two hoots about that. It can see in sixteen different wavelengths of light compared to our puny three,3 which is rather more useful to them than all the culture and self-regard that we have mustered over the millennia.

  Nevertheless, a book is a thing that typifies the gap between us and all other beasts. It is the sharing of information generated by thousands of others, almost none of whom I am closely related to. I have studied their ideas, and recorded them into a tool of almost unimaginable complexity, so that our minds might be enriched with this collection of stories that are new and hopefully interesting to anyone who cares to pick it up.

  This is a book about the paradox of how we became us. It is an exploration of an evolution that bestowed enormous powers of intellect on an otherwise average ape, to create tools, art, music, science and engineering. Through old bones and, nowadays, genetics, we know about the mechanics of our evolutionary journey through the eons (though there is so much still to discover), but we know far less about the development of our behaviour, of our minds, and of the way that we uniquely evolved into the cultural and social beings that we are today.