Darwin's Island Part 1

Darwin's Island.

by STEVE JONES.

INTRODUCTION.

THE DARWIN ARCHIPELAGO.

Charles Darwin, as every schoolchild knows, saw the finches of the Galapagos in the years he spent there while employed as official naturalist on HMS Beagle Beagle. Each island had its own species, and Darwin soon worked out that they shared descent from a common ancestor; that they were a product of evolution. On his return to England he at once published his theory in his book Origin of the Species Origin of the Species, which went on to prove that men had descended from chimpanzees. Nature, red in tooth and claw, had used the survival of the fittest to weed out the imperfect and, with h.o.m.o sapiens h.o.m.o sapiens at the top of the evolutionary tree, had achieved her desired end. Racked by guilt at replacing the doctrines of the Church with a joyless vision of man as a shaven primate in an amoral universe, Charles Darwin retired into obscurity. He repented his blasphemy on his deathbed and was buried as a venerable and almost forgotten savant whose work - like that of so many famous scientists - had been completed while he was still a young man. at the top of the evolutionary tree, had achieved her desired end. Racked by guilt at replacing the doctrines of the Church with a joyless vision of man as a shaven primate in an amoral universe, Charles Darwin retired into obscurity. He repented his blasphemy on his deathbed and was buried as a venerable and almost forgotten savant whose work - like that of so many famous scientists - had been completed while he was still a young man.

That is an entire parody of the truth. Darwin was not a hired biologist but paid for his own trip as gentleman-companion to the Beagle Beagle's captain. He spent but five weeks of the five-year voyage in the Galapagos, with just half the time pa.s.sed on sh.o.r.e, on only four of the dozen or so members of the group. He had little interest in his collection of finches and lumped their corpses together as a jumbled ma.s.s without even making a note of where they came from. Many of the famous birds live on several islands rather than one. Two decades pa.s.sed before the publication of The Origin of Species The Origin of Species (in which the word 'evolution' does not appear) and in that time its author wrote several substantial books. The phrase 'the survival of the fittest' is not his but was invented by the philosopher Herbert Spencer to summarise the notion of natural selection, the central element of evolutionary theory. The b.l.o.o.d.y fangs and fingernails of Mother Nature were themselves thought up by Tennyson a decade earlier not as a philosophy of life but in memory of the death of a friend. Evolution has no end in view and men do not descend from chimps, although the two share a common ancestor (an idea not explored by Darwin for a dozen years after (in which the word 'evolution' does not appear) and in that time its author wrote several substantial books. The phrase 'the survival of the fittest' is not his but was invented by the philosopher Herbert Spencer to summarise the notion of natural selection, the central element of evolutionary theory. The b.l.o.o.d.y fangs and fingernails of Mother Nature were themselves thought up by Tennyson a decade earlier not as a philosophy of life but in memory of the death of a friend. Evolution has no end in view and men do not descend from chimps, although the two share a common ancestor (an idea not explored by Darwin for a dozen years after The Origin The Origin). The Church soon accommodated his ideas, which, as most clerics realised, have no relevance to religion and the deathbed conversion is a simple falsehood, even if the great naturalist was buried in Westminster Abbey, where he still lies, trampled by tourists.

The most widespread error is to a.s.sume that the Beagle Beagle voyage marked the end of Charles Darwin's scientific career. In fact, in the four decades that remained to him after he came home from the wilds in 1836, Captain Fitzroy's gentleman-companion worked as hard as or harder than he had as a young man. He soon purchased Down House, south of London, in the eponymous village (whose name gained a terminal 'e' at the insistence of the Post Office, a rule that Darwin ignored). voyage marked the end of Charles Darwin's scientific career. In fact, in the four decades that remained to him after he came home from the wilds in 1836, Captain Fitzroy's gentleman-companion worked as hard as or harder than he had as a young man. He soon purchased Down House, south of London, in the eponymous village (whose name gained a terminal 'e' at the insistence of the Post Office, a rule that Darwin ignored).

At first he saw the place as dull and unattractive enough, but before long the house was transformed, with the help of his considerable fortune, into a grand but comfortable mansion. Its owner settled in the land of his birth and never left again: uxorious, paternal and reluctant to leave his extensive garden except on forays to test his theories and, now and again, to search for better health. As he wrote, with some satisfaction, many years after moving in: 'Few persons can have lived a more retired life than we have done . . . My life goes on like clock-work and I am fixed on the spot where I shall end it.' So settled was he that he described his profession as 'farmer' in the Bagshawe's Directory Directory of the time. Great Britain was the first and last of the forty islands he visited and the patriarch of Downe studied its natural history in far more detail than he had that of anywhere else. His own county of Kent - the Garden of England - was as much, or more, a place of discovery than had been the jungles of the Amazon or the stark cinders of the Galapagos. The British Isles were where Charles Darwin built his reputation. of the time. Great Britain was the first and last of the forty islands he visited and the patriarch of Downe studied its natural history in far more detail than he had that of anywhere else. His own county of Kent - the Garden of England - was as much, or more, a place of discovery than had been the jungles of the Amazon or the stark cinders of the Galapagos. The British Isles were where Charles Darwin built his reputation.

This book is about the disregarded Darwin, the most ill.u.s.trious figure in biology, and about his years of work on the plants, animals and people that make their home in the land of his birth. The Origin of Species The Origin of Species is, without doubt, the most famous book in science. It celebrates its hundred-and-fiftieth anniversary in 2009, which marks in addition the author's bicentenary. is, without doubt, the most famous book in science. It celebrates its hundred-and-fiftieth anniversary in 2009, which marks in addition the author's bicentenary.

To remember that magnum opus magnum opus alone would be as foolish as to celebrate Shakespeare just as the author of alone would be as foolish as to celebrate Shakespeare just as the author of Hamlet. Hamlet. The great naturalist's lifelong labours generated an archipelago of information; a set of connected observations that together form a harmonious whole. He wrote six million words in nineteen published works, hundreds of scientific papers and innumerable letters, fourteen thousand of which survive. Although - because of the famous note from Alfred Russel Wallace that bounced him into writing The great naturalist's lifelong labours generated an archipelago of information; a set of connected observations that together form a harmonious whole. He wrote six million words in nineteen published works, hundreds of scientific papers and innumerable letters, fourteen thousand of which survive. Although - because of the famous note from Alfred Russel Wallace that bounced him into writing The Origin - The Origin - he never finished his he never finished his magnum opus magnum opus, his 'big species book', much of its planned contents appeared as a series of separate volumes throughout his lifetime. Biology emerged from that gargantuan effort as a unitary subject, linked by Charles Darwin's grand idea of common ancestry, of evolution. The volumes that poured from his comfortable study were guidebooks that made sense of a whole new science. They allowed its students to navigate what had, before his day, been an uncharted labyrinth of shoals, reefs and remote islets of apparently unrelated facts.

The Origin itself was in truth no more than a prologue to the great man's career. It is as much a work of reportage as it is of research. Most of his other publications are, in contrast, based on his own observations and experiments and explore, with his trademark enthusiasm, what appear at first sight to be almost unrelated aspects of the natural world. Darwin's domestic works, as they might be called, are, in order of appearance and with t.i.tles somewhat truncated: itself was in truth no more than a prologue to the great man's career. It is as much a work of reportage as it is of research. Most of his other publications are, in contrast, based on his own observations and experiments and explore, with his trademark enthusiasm, what appear at first sight to be almost unrelated aspects of the natural world. Darwin's domestic works, as they might be called, are, in order of appearance and with t.i.tles somewhat truncated: Barnacles Barnacles (in four volumes), (in four volumes), Orchids and Insects Orchids and Insects, Variation under Domestication Variation under Domestication, The Descent of Man The Descent of Man, Expression of the Emotions Expression of the Emotions, Insectivorous Plants Insectivorous Plants, Climbing Plants Climbing Plants, Cross and Self-Fertilisation Cross and Self-Fertilisation , , Forms of Flowers Forms of Flowers, Movement in Plants Movement in Plants and and Formation of Vegetable Mould by Earthworms. The Origin Formation of Vegetable Mould by Earthworms. The Origin has but a single ill.u.s.tration, but most of the others are filled with line drawings, engravings and plates, almost five hundred altogether (and some find a place in the present pages). has but a single ill.u.s.tration, but most of the others are filled with line drawings, engravings and plates, almost five hundred altogether (and some find a place in the present pages). The Expression of the Emotions The Expression of the Emotions was one of the very first scientific books to be ill.u.s.trated with photographs. was one of the very first scientific books to be ill.u.s.trated with photographs.

His literary oeuvre was aimed at a wide audience and is set out in good, plain Victorian prose. He wrote to Thomas Henry Huxley in 1865 that 'I sometimes think that general and popular Treatises are almost as important for the progress of science as original work.' Charles Darwin was the first popular science writer - and his publisher appreciated as much for he gave The Origin The Origin equal billing with Samuel Smiles's quintessentially Victorian work equal billing with Samuel Smiles's quintessentially Victorian work Self-Help Self-Help, which appeared on the same day. The author himself realised the public's interest in his work for he was one of the first among that dubious breed of scribblers to negotiate a pre-publication cash advance before settling down at his desk. Unlike most of his intellectual descendants, Darwin's command of foreign languages was good enough to allow him to pick up some of the atrocities committed on his ma.n.u.scripts by their translators and he spent much time anguis.h.i.+ng about quite what French or German phrase best approximated to his central notion of 'natural selection'.

Here I attempt to bring his lesser-known writings up to date for the modern age and to place the world's pre-eminent biologist firmly in the context of his native land. His literary canon makes sense only when considered as a whole. At first sight its subjects seem almost disconnected - earthworms, inbreeding, barnacles, plant hormones, domestication, insect-eating plants and the expressions of joy or despair in dogs, apes and men - but in truth all share a theme: the power of small means, given time, to produce gigantic ends. Fond family man as he was, he saw no gulf between the powers that had made his wife and children and those at work elsewhere. His concerns about the risks of marrying his cousin were tested with experiments on flowers. In the same way, an interest in the emotions of animals led to a comparison of the expressions of his infant son with those of dogs and apes. Different as his children might be from such humble creatures, all had emerged through the action of the same biological forces; through evolution, or 'descent with modification'. The notion, and his willingness to apply it to ourselves, outraged some of his fellows. It leaves many people uncomfortable today.

Biology has plenty of heroes but Charles Darwin is unique, for he was a pioneer in so many of its branches. He became a better scientist as he grew older for he began to test ideas with his own hands-on research, much of it far ahead of its time, rather than collating the results of others, brilliant as the synthesis might be; as he said later in life, 'I am like a gambler, & love a wild experiment.'

A good portion of the educated public has heard of The Origin The Origin and and The Voyage of the Beagle The Voyage of the Beagle but his other works are almost unknown. Most biologists are familiar with at least some of them for each volume is a milestone in their profession. The but his other works are almost unknown. Most biologists are familiar with at least some of them for each volume is a milestone in their profession. The Earthworms Earthworms epic founded modern soil science, epic founded modern soil science, Emotions Emotions saw the dawn of comparative psychology while saw the dawn of comparative psychology while Cross and Self-Fertilisation Cross and Self-Fertilisation and and Forms of Flowers Forms of Flowers were each an attempt to understand the origin of s.e.x. The experiments described in were each an attempt to understand the origin of s.e.x. The experiments described in Movement in Plants Movement in Plants gave the first clue to the existence of hormones (although the word had not been invented and their discovery in animals had to wait thirty years). Their author also wrote on carnivorous plants, on the links between insects and orchids, and on the origin of our domestic plants and animals (and there he grappled with the nature of heredity, and almost got it right, with talk of crosses between round and wrinkled peas). Even his four books on barnacles, obscure as they appear, are important, for they showed that juvenile forms reveal more about relatedness than do adults and that bodies as complicated as our own are built on a simple plan. For barnacles and all other creatures his mechanism of natural selection generates organs of impressive perfection not by design but by tinkering with whatever raw material is available. gave the first clue to the existence of hormones (although the word had not been invented and their discovery in animals had to wait thirty years). Their author also wrote on carnivorous plants, on the links between insects and orchids, and on the origin of our domestic plants and animals (and there he grappled with the nature of heredity, and almost got it right, with talk of crosses between round and wrinkled peas). Even his four books on barnacles, obscure as they appear, are important, for they showed that juvenile forms reveal more about relatedness than do adults and that bodies as complicated as our own are built on a simple plan. For barnacles and all other creatures his mechanism of natural selection generates organs of impressive perfection not by design but by tinkering with whatever raw material is available.

The Descent of Man, and Selection in Relation to s.e.x and Selection in Relation to s.e.x, to give its full t.i.tle, stands rather apart from the rest. The book appeared in 1871 and was both the first real treatment of human evolution and an introduction to the importance of s.e.xual conflict in evolution. It sets out the entire Darwinian argument with reference to a single group of creatures: man and his relatives. Descent Descent, like The Origin of Species The Origin of Species, is in the main a compilation of the results of others. Even so, it fits well into what might be called the Down House School and I use it here as an introduction to the world of modern evolutionary biology as ill.u.s.trated by ourselves and our primate relatives. The study of our past has been transformed. If the author of The Origin The Origin were to rewrite that famous work today he would turn for many of his examples not to pigeons and tortoises, nor to worms and barnacles, but to his fellow citizens. were to rewrite that famous work today he would turn for many of his examples not to pigeons and tortoises, nor to worms and barnacles, but to his fellow citizens. The Origin The Origin's sole mention of h.o.m.o sapiens h.o.m.o sapiens, the tentative claim that 'Light will be thrown on the origin of man and his history', has been wonderfully upheld. It shows how the truths glimpsed by Darwin now unite the whole science of life.

Here I attempt to update all those topics for today. I append an envoi envoi with a look at the biological world of the twenty-first century compared with its state in 1859. In the tradition of the great naturalist himself, who was dubious about the many infantile attempts to apply his ideas to society (as in a newspaper's claim that his work proved that 'might is right & therefore that Napoleon is right & every cheating tradesman is also right'), I avoid as far as possible any discussion of the relevance of Darwinism to the human predicament. I also steer clear of the empty arguments about its interactions with religion. The struggle to separate science from theology still fascinates a few, but most scientists have no interest in it (although there are exceptions, for the Victorian biologist Thomas Henry Huxley felt that 'Extinguished theologians lie about the cradle of every science as the strangled snakes besides that of Hercules'). Today's biology in its success emphasises how little relevance it has to the issues so often, and so tediously, discussed by non-biologists. As Darwin put it in with a look at the biological world of the twenty-first century compared with its state in 1859. In the tradition of the great naturalist himself, who was dubious about the many infantile attempts to apply his ideas to society (as in a newspaper's claim that his work proved that 'might is right & therefore that Napoleon is right & every cheating tradesman is also right'), I avoid as far as possible any discussion of the relevance of Darwinism to the human predicament. I also steer clear of the empty arguments about its interactions with religion. The struggle to separate science from theology still fascinates a few, but most scientists have no interest in it (although there are exceptions, for the Victorian biologist Thomas Henry Huxley felt that 'Extinguished theologians lie about the cradle of every science as the strangled snakes besides that of Hercules'). Today's biology in its success emphasises how little relevance it has to the issues so often, and so tediously, discussed by non-biologists. As Darwin put it in The Descent of Man The Descent of Man: 'We are not here concerned with hopes or fears, only with the truth as far as our reason allows us to discover it.' Science can do that, and no more.

My eminent predecessor at University College London, the n.o.bel Prize-winner Peter Medawar, in an acerbic comment on the relative merits of students of science and the arts, said of Watson and Crick (of double helix fame) that 'Not only were they clever, they had something to be clever about.' Not only did Charles Darwin travel, he had something to travel for. The joy of the Beagle Beagle voyage was that it had a point. For a real adventurer, to travel hopefully is not enough: some end must be in view. As he wrote in the last pages of his account of the journey: 'If a person asked my advice before undertaking a long voyage, my answer would depend upon his possessing a decided taste for some branch of knowledge, which could by this means be advanced.' voyage was that it had a point. For a real adventurer, to travel hopefully is not enough: some end must be in view. As he wrote in the last pages of his account of the journey: 'If a person asked my advice before undertaking a long voyage, my answer would depend upon his possessing a decided taste for some branch of knowledge, which could by this means be advanced.'

Darwin's odysseys, from the Galapagos to West Wales, play an important part in all his books, as they did in the author's life. The Beagle Beagle crossed nearly fifty thousand kilometres of ocean but his British journeys covered almost as much country. His work was always tied to where he found himself, whether in a rain forest or a suburb. Many of his compositions emerge from a kind of Grand Tour of the British Isles. His very first memory, as recounted in his autobiography, was of a visit to Abergele for the sea-bathing at the age of four. Six years later he was back on the Welsh coast at Towyn, where he noted some 'curious insects' (black and red Burnet Moths) not seen around Shrewsbury. Unlike the many naturalists of those times who filled cabinets with b.u.t.terflies or sh.e.l.ls to make a biological stamp-collection, he wondered, even as a child, quite why they were found in one place and not another. crossed nearly fifty thousand kilometres of ocean but his British journeys covered almost as much country. His work was always tied to where he found himself, whether in a rain forest or a suburb. Many of his compositions emerge from a kind of Grand Tour of the British Isles. His very first memory, as recounted in his autobiography, was of a visit to Abergele for the sea-bathing at the age of four. Six years later he was back on the Welsh coast at Towyn, where he noted some 'curious insects' (black and red Burnet Moths) not seen around Shrewsbury. Unlike the many naturalists of those times who filled cabinets with b.u.t.terflies or sh.e.l.ls to make a biological stamp-collection, he wondered, even as a child, quite why they were found in one place and not another.

As he grew older, natural history became an all-embracing pa.s.sion. His early enjoyment of literature, art and music disappeared and he wrote that 'I have tried lately to read Shakespeare and found it so intolerably dull that it nauseated me.' His preferred reading consisted of romantic novels (the sillier the story, the better, said his children) and he sold off his family heirlooms of Wedgwood pottery and Flaxman reliefs. He could make out 'absolutely nothing' of what merit there was in a collection of Turner watercolours. 'My mind', he wrote, 'seems to have become a kind of machine for grinding general laws out of a large collection of facts, but why this should have caused the atrophy of that part of the brain alone, on which the higher tastes depend I cannot conceive' (although he did send the Expression of the Emotions Expression of the Emotions book to art journals for review, where it was criticised for its insensitivity to the nature of Art). book to art journals for review, where it was criticised for its insensitivity to the nature of Art).

That obsession with science allowed Charles Darwin's juvenile interest in the insects of England and Wales to grow into a lifelong exploration of the biology and geology of his native island. He published his first scientific paper, on the eggs of an animal found in the Firth of Forth, in the twelve grey months he spent in Edinburgh. After a brief visit to Dublin, the young enthusiast then moved to Cambridge, where he spent many days knee-deep in bogs and fens in the search for specimens. Just before the departure of the Beagle Beagle, he travelled for three weeks across North Wales from Shrewsbury to Conwy and Barmouth with the geologist Adam Sedgwick, who taught him the elements of mapping so useful on the voyage. On his return he set off again to Scotland, where, in his first major scientific paper, he made a frightful error in his evaluation of a series of parallel shelves or 'roads' in Glen Roy as wave-cut beaches rather than the sh.o.r.es of drained glacial lakes (as he wrote many years later, 'I am ashamed of it'). Later in life he criss-crossed Britain to pursue his researches or to take his family on holiday, or to escape the epidemics of infection that now and again swept through Downe (and killed two of his own children). They went to Wales, to the Isle of Wight (where he met Alfred, Lord Tennyson), to Torquay, to the Lake District (an audience there with Ruskin), to Stonehenge, to the heathlands of England and to a variety of grand mansions across the kingdom. Often, his experimental subjects - pots of orchids or of insect-eating plants - travelled with the family, at considerable inconvenience. He had plenty of time to explore the British Isles for in his forty years at Down House Charles Darwin spent two thousand nights away from home - the equivalent of a day a week. A few of his trips lasted a month and more.

Some of his travels were in search of science, but many were a quest for health. He became chronically ill very soon after his return from the Beagle Beagle trip and his heavy use of snuff and tobacco did nothing to improve his well-being. Darwin visited spas in Great Malvern, in Guildford and in Ilkley (where he received the first copy of trip and his heavy use of snuff and tobacco did nothing to improve his well-being. Darwin visited spas in Great Malvern, in Guildford and in Ilkley (where he received the first copy of The Origin The Origin). His later years were marked by a series of bizarre attempts to remedy his feeble state (even if he did write that illness, 'though it has annihilated several years of my life, has saved me from the distractions of society and amus.e.m.e.nt'). The main symptom was vomiting, often brought on by stress, with the rushed last chapter of The Origin The Origin sparking off a severe episode that caused great prostration of mind and body. So severe were the attacks that he declined some invitations to stay in friends' houses on the grounds that 'my retching is apt to be extremely loud'. sparking off a severe episode that caused great prostration of mind and body. So severe were the attacks that he declined some invitations to stay in friends' houses on the grounds that 'my retching is apt to be extremely loud'.

He tried Condy's Ozonised Fluid, 'enormous quant.i.ties of chalk, magnesia & carb of ammonia', and rubber bags filled with ice and worn next to the spine. Nothing worked (although he learned to play billiards at one of the establishments and became a devotee of the pastime, which helped him to relax and, as he said, 'drives the horrid species out of my head'). The author of The Origin The Origin was a victim of the Victorian 'Demon of Dyspepsia' and was joined in that unhappy throng by Thomas Carlyle, George Eliot, Charles d.i.c.kens, Florence Nightingale and the evolutionists T. H. Huxley, Alfred Russel Wallace and Herbert Spencer, together with his own brother Erasmus. Their troubles funded several pharmaceutical fortunes (including that of Henry Wellcome, which later helped pay for that Darwinian triumph, the sequence of human DNA). What his condition might have been is not known: a supposed conflict between Christian belief and rationalism, or a parasite picked up in Brazil or even, some say, the obsessive swallowing of air. He was diagnosed as having 'waterbrash' - heartburn, in modern parlance, the reflux of acid from the stomach - which can result from an ulcer. Dyspepsia's nausea, depression and la.s.situde are, we know today, caused by a bacterium. The bug that swept through Victoria's intellectuals might now be cured with a simple pill. was a victim of the Victorian 'Demon of Dyspepsia' and was joined in that unhappy throng by Thomas Carlyle, George Eliot, Charles d.i.c.kens, Florence Nightingale and the evolutionists T. H. Huxley, Alfred Russel Wallace and Herbert Spencer, together with his own brother Erasmus. Their troubles funded several pharmaceutical fortunes (including that of Henry Wellcome, which later helped pay for that Darwinian triumph, the sequence of human DNA). What his condition might have been is not known: a supposed conflict between Christian belief and rationalism, or a parasite picked up in Brazil or even, some say, the obsessive swallowing of air. He was diagnosed as having 'waterbrash' - heartburn, in modern parlance, the reflux of acid from the stomach - which can result from an ulcer. Dyspepsia's nausea, depression and la.s.situde are, we know today, caused by a bacterium. The bug that swept through Victoria's intellectuals might now be cured with a simple pill.

Later in life, in part because of his health, the paterfamilias of Down House spent longer and longer periods without leaving home. He fed his household with fifty-three distinct varieties of gooseberries and three of cabbage. In his garden he carried out many experiments, helped by William Brooke, his 'gloomy gardener' (who was seen to laugh just once, when a boomerang broke a cuc.u.mber frame). The naturalist's tale ends, in the tradition of the cla.s.sics, with the hero's death and his desire to join his beloved earthworms in the 'sweetest place on Earth', the village churchyard at Downe - a wish frustrated by fame, the establishment and the Abbey.

Darwin's Island retraces some of Darwin's steps and moves his discoveries forward by a century and more. It will, I hope, help bring his less well-known work into the third millennium. Several people have helped in the preparation of this book. David Leibel, Michael Morgan, Kay Taylor and Anna Trench made helpful comments on parts of it. I thank them for their help. retraces some of Darwin's steps and moves his discoveries forward by a century and more. It will, I hope, help bring his less well-known work into the third millennium. Several people have helped in the preparation of this book. David Leibel, Michael Morgan, Kay Taylor and Anna Trench made helpful comments on parts of it. I thank them for their help.

Three of my earlier volumes - on coral reefs, on the nature of maleness and on the theory of evolution itself - pay homage to the founder of the science of life, and each is an attempt to update his ideas for the modern age. There could be no better way to honour the most famous of all biologists at this time of concentrated attention on his history than to give his less celebrated works the exposure they deserve. For Charles Darwin, the five Beagle Beagle years that became part of Britain's intellectual legacy led to four decades of intense labour within the confines of his native land. In that modest group of islands he underwent a second great voyage: not of the body but of the mind. This book traces that journey from its beginning to its end. years that became part of Britain's intellectual legacy led to four decades of intense labour within the confines of his native land. In that modest group of islands he underwent a second great voyage: not of the body but of the mind. This book traces that journey from its beginning to its end.

CHAPTER I.

THE QUEEN'S ORANG-UTAN

In 1842 Queen Victoria went to London Zoo. She was less than amused: 'The Orang Outang is too wonderful . . . he is frightfully, and painfully, and disagreeably human.' The animal was not a male but a female called Jenny and Charles Darwin had, some years earlier, visited its mother. He too spotted the resemblance between the apes on either side of the bars. The young biologist scribbled in his notebook that 'Man in his arrogance thinks himself a great work. More humble and I believe true to consider him created from animals.' Seventeen years after Victoria's visit, in 1859, he published the theory that proved the Queen's kins.h.i.+p, and his own, to Jenny, to every inmate of the Zoological Gardens and to all the inhabitants of the Earth.

The Origin of Species caused uproar among the Empress of India's subjects. Her Chancellor, Benjamin Disraeli, asked famously: 'Is man an ape or an angel? My Lord, I am on the side of the angels. I repudiate with indignation and abhorrence these new fangled theories.' Many of his fellow citizens agreed. Even so, the notion at once entered public discourse (and caused uproar among the Empress of India's subjects. Her Chancellor, Benjamin Disraeli, asked famously: 'Is man an ape or an angel? My Lord, I am on the side of the angels. I repudiate with indignation and abhorrence these new fangled theories.' Many of his fellow citizens agreed. Even so, the notion at once entered public discourse (and Punch Punch devoted its 1861 Christmas annual to gorilla-like humans and their opposites). In time, and with some reluctance, the notion that every Briton, high or low, shared descent with the rest of the world was accepted. A quarter of a century on, W. S. Gilbert penned the deathless line that 'Darwinian man, though well behaved, at best is only a monkey shaved' and the idea of devoted its 1861 Christmas annual to gorilla-like humans and their opposites). In time, and with some reluctance, the notion that every Briton, high or low, shared descent with the rest of the world was accepted. A quarter of a century on, W. S. Gilbert penned the deathless line that 'Darwinian man, though well behaved, at best is only a monkey shaved' and the idea of h.o.m.o sapiens h.o.m.o sapiens as a depilated ape became part of popular culture, where it belongs. Victoria herself congratulated one of her daughters, the crown princess of Prussia, for turning to as a depilated ape became part of popular culture, where it belongs. Victoria herself congratulated one of her daughters, the crown princess of Prussia, for turning to The Origin The Origin: 'How many interesting, difficult books you read. It would and will please beloved Papa.'

As the Queen had noticed, the physical similarity of men to apes is clear. In 1859, Charles Darwin came up with the reason why. A certain caution was needed to promote the idea that what had made animals had also produced men and women, and he waited for twelve years before he expanded on the subject. The Descent of Man The Descent of Man describes how - and why - describes how - and why - h.o.m.o sapiens h.o.m.o sapiens shares its nature with other primates. The book uses our own species as an exemplar of evolution. shares its nature with other primates. The book uses our own species as an exemplar of evolution.

To the founder of modern biology, man obeyed the same evolutionary rules as all his kin and shared much of his physical being with them; as the book says, in its final paragraph, he still bears 'the indelible stamp of his lowly origin'. In moral terms h.o.m.o sapiens h.o.m.o sapiens was something more: '. . . of all the differences between man and the lower animals, the moral sense or conscience is by far the most important. This sense . . . is summed up in that short but imperious word "ought," so full of high significance. It is the most n.o.ble of all the attributes of man, leading him without a moment's hesitation to risk his life for that of a fellow-creature.' No ape understands the meaning of 'ought', a word pregnant with notions quite alien to every species apart from one. Even so, despite that essential and uniquely human attribute, every ape - and we are among them - is, like every other creature, the product of a common biological mechanism. was something more: '. . . of all the differences between man and the lower animals, the moral sense or conscience is by far the most important. This sense . . . is summed up in that short but imperious word "ought," so full of high significance. It is the most n.o.ble of all the attributes of man, leading him without a moment's hesitation to risk his life for that of a fellow-creature.' No ape understands the meaning of 'ought', a word pregnant with notions quite alien to every species apart from one. Even so, despite that essential and uniquely human attribute, every ape - and we are among them - is, like every other creature, the product of a common biological mechanism.

The logic of evolution is simple. There exists, within all plants and animals, variation pa.s.sed from one generation to the next. More individuals are born than can live or breed. As a result, there develops a struggle to stay alive and to find a mate. In that battle, those who bear certain variants prevail over others less well endowed. Such inherited differences in the ability to transmit genes - natural selection, as Darwin called it - mean that the advantageous forms become more common as the generations succeed each other. In time, as new versions acc.u.mulate, a lineage may change so much that it can no longer exchange genes with those that were once its kin. A new species is born.

Natural selection is a factory that makes almost impossible things. It manufactures what seems like design with no need for a designer. Evolution builds complicated organs like the eye, the ear or the elbow by piecing together favoured variants as they arise. Almost as an afterthought, it generates new forms of life.

Its tale as told in The Origin of Species The Origin of Species turns on the efforts of farmers as they develop new breeds from old, on changes in wild creatures exposed to the rigours of nature and the demands of the opposite s.e.x, on the tendency of isolated places to evolve unique forms, and on the silent words of the fossils that tell of a planet as it was before evolution moved on. Its pages speak of the embryo as a key to the past and of how structures no longer of value and others that appear almost too perfect are each testimony of the power of natural selection. The geography of life, on islands, continents and mountains, is also evidence of the common descent of mushrooms, mice and men. Most of all, life's diversity can be arranged into a series of groups arranged within groups, of ever-decreasing affinity, as a strong hint that they split apart from each other longer and longer ago. turns on the efforts of farmers as they develop new breeds from old, on changes in wild creatures exposed to the rigours of nature and the demands of the opposite s.e.x, on the tendency of isolated places to evolve unique forms, and on the silent words of the fossils that tell of a planet as it was before evolution moved on. Its pages speak of the embryo as a key to the past and of how structures no longer of value and others that appear almost too perfect are each testimony of the power of natural selection. The geography of life, on islands, continents and mountains, is also evidence of the common descent of mushrooms, mice and men. Most of all, life's diversity can be arranged into a series of groups arranged within groups, of ever-decreasing affinity, as a strong hint that they split apart from each other longer and longer ago.

The Descent of Man uses that logic to disentangle the history of a single species. Unique as it might think itself, uses that logic to disentangle the history of a single species. Unique as it might think itself, h.o.m.o sapiens h.o.m.o sapiens is animal like all others. The book's famous last sentence reads, in full: 'I have given the evidence to the best of my ability: and we must acknowledge, as it seems to me, that man with all his n.o.ble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his G.o.d-like intellect which has penetrated into the movements and const.i.tution of the solar system - with all these exalted powers - Man still bears in his bodily frame the indelible stamp of his lowly origin.' is animal like all others. The book's famous last sentence reads, in full: 'I have given the evidence to the best of my ability: and we must acknowledge, as it seems to me, that man with all his n.o.ble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his G.o.d-like intellect which has penetrated into the movements and const.i.tution of the solar system - with all these exalted powers - Man still bears in his bodily frame the indelible stamp of his lowly origin.'

In 1871 - and even in 1971 - the evidence for that final and provocative statement was weak indeed. Now, everything has changed. The entire evolutionary case can be made in terms of ourselves and our relatives; of apes and monkeys, of chimps and gorillas, and of men and women. Our new ability to look at genes, cells, tissues and organs in exquisite detail means that we know more about the human past than about that of any other species. Evolution is best viewed through our own eyes; and not just because we are all interested in where we came from but because advances in science mean that h.o.m.o sapiens h.o.m.o sapiens has become the embodiment of every evolutionary idea. Darwin's theory has not altered much in the century and a half since it was proposed. The technology used to study it has, on the other hand, been transformed. has become the embodiment of every evolutionary idea. Darwin's theory has not altered much in the century and a half since it was proposed. The technology used to study it has, on the other hand, been transformed.

Technical as they have become, the tools used today to examine the past would have been familiar in their nature, if not in their details, to biologists of the nineteenth century. Charles Darwin was, among his many talents, a proficient anatomist. He used changes in the physical structure of pigeons, pigs and people as evidence for his theory. The first chapter of The Descent of Man The Descent of Man is a somewhat ponderous account of the differences between the bones and bodies of men and apes. Dissection, once at the centre of biology (and biologists of a certain age still flinch at the smell of formalin), not long ago appeared antiquated, but now it looks very modern. Molecular biology is no more than comparative anatomy plus a mountain of cash. Its chemical scalpels cut up creatures into thousands of millions of individual letters of DNA code. Those who wield them have shown beyond all doubt the truth behind Queen Victoria's fear that the bodily frame of Jenny the orang-utan was proof of the common ancestry of humans with apes and with far more. is a somewhat ponderous account of the differences between the bones and bodies of men and apes. Dissection, once at the centre of biology (and biologists of a certain age still flinch at the smell of formalin), not long ago appeared antiquated, but now it looks very modern. Molecular biology is no more than comparative anatomy plus a mountain of cash. Its chemical scalpels cut up creatures into thousands of millions of individual letters of DNA code. Those who wield them have shown beyond all doubt the truth behind Queen Victoria's fear that the bodily frame of Jenny the orang-utan was proof of the common ancestry of humans with apes and with far more.

The Human Genome Project - the scheme to read off our own DNA sequence - set the seal on an enterprise which began in the sixteenth century when Vesalius opened the heart and discovered that it had four chambers rather than the three insisted on by the Greeks. Its completion was announced in 2000 and again in 2003, 2006 and 2008 (and some parts of the double helix still remain unread). A science that had been in its infancy a mere description of bones and muscles became an adolescent when The Origin of Species The Origin of Species showed how shared structure was evidence of common descent. It has at last matured. The anatomy of DNA has become the key to the history of life. showed how shared structure was evidence of common descent. It has at last matured. The anatomy of DNA has become the key to the history of life.

In a gla.s.s-fronted cabinet at University College London resides the stuffed body of the eighteenth-century philosopher Jeremy Bentham, the 'greatest good for the greatest number' man. His Auto-Icon, as he called it, was an attempt at a memorial that would cost less than the showy shrines then fas.h.i.+onable. Bentham was convinced that his idea would catch on. Two centuries later, it did. James Watson - the surviving half of the duo who unwound the double helix - was presented with his own auto-icon, a compact disc of his entire DNA sequence, which he can, if he wishes, display for public edification in a small plastic case.

Watson's essence is coded into a tangled ma.s.s of intricate chemistry. The egg that made him contained two metres of DNA and each of the billions of cells that descend from it as his body grows and ages has a copy. Each of those molecular sentences is written in three thousand two hundred million letters, the four bases of the familiar genetic code. Twenty years ago, when the scheme to read the whole lot off was proposed, it took months to decipher the number of letters found in this paragraph. The molecule was sliced into random bits, each was read from end to end and the whole genome st.i.tched together with a search for places where the fragments overlap. Such methods are antique. Today's machines pick up flashes of light from molecules tagged with fluorescent dyes, each base with its own colour, and squeezed one at a time through tiny pores. It takes no more than a few hours to read off a piece as long as this entire book, which itself contains less than one part in several thousand of the whole content of the human genome. Soon it will become possible to sequence single molecules rather than multiple copies, as is now necessary, and enthusiasts speak of machines that will read off a million DNA bases a second.

The first human sequence cost up to a billion dollars and Watson's version was auctioned off for a million. In 2008 the Knome Corporation offered to read off the DNA of anybody with a spare $350,000. In fact, the whole lot can now be done for a fraction of that sum. Within five years the price will drop to a few thousand dollars per genome and it will become possible to decipher the DNA of any creature at nominal cost. The web of kins.h.i.+p that binds life together will then be revealed in all its details.

The raw material of evolution is, in its physical structure as an intertwined helix, simple or even elegant, but in its biology is entirely the opposite. In its details DNA is, frankly, a mess, for natural selection has been forced to build upon what it already has. Life did not emerge from engineering, but from expedience. The Darwinian machine has no strategy and can never look forward. Its tactics are based on the moment, and the genomes it makes, like the creatures they code for, are the products of a set of short-term fixes. James Watson's molecule is marked by redundancy, decay and the scars of battles long gone. Genes - like cells, guts and brains - work, but only just.

Human DNA contains long stretches that appear to be useless and numerous sections that are mirror-images of each other. Repet.i.tion is everywhere: of particular genes into families that carry out similar tasks and of multiplied lengths of material that seems redundant. The remnants of viruses make up almost half the total and the remainder is littered by the decayed hulks of ancient and once functional structures. All but one part in fifty of the genome was, as a result, once (mistakenly) dismissed as biological garbage.

The genes themselves have become blurred and ambiguous as we learn more. There are far fewer than expected when the genome project was proposed - just over twenty thousand rather than the mult.i.tude then a.s.sumed to be essential. Some overlap with each other or say different things when read in opposite directions or when active in different tissues. Many contain inserted sequences of DNA that looks as if they have no function (although some of the supposed junk does a useful job while other sections cause disease should they wake up and s.h.i.+ft position). Plenty of questions remain. How important is the part - often a small part - of each gene that codes for proteins compared with the on and off switches, the accelerators and brakes, and the rest of the control machinery? We do not know.

Even the size of the package makes little sense. A chicken has slightly less DNA than does a n.o.bel laureate but half its genes are identical, or almost so, to our own - evidence, given that we last shared an ancestor three hundred million years ago, of how conservative evolution can be. A tiny plant called Arabidopsis Arabidopsis, a relative of the Brussels sprout, has more genes than either. All this says more about how hard it can be to define what a gene actually is than about the talents of sprout versus sentient being.

Eight decades pa.s.sed between Vesalius' dissection of the heart and the discovery of the circulation of the blood. The genome is now in that transitional period. DNA's nuts and bolts (and even some of its bells and whistles) have been dismantled, but most of those who work on it still study structure without much insight into function. William Harvey (the circulation man) saw the heart as a mere pump, and understood nothing of its exquisite system of control. Genes are much the same. Each is linked into a network with others and responds to messages from both within and outside the cell. The path from instruction to product is a labyrinth, rather than a straight line. The proteins that pour from the cell's biological factories are not simple blocks that slot together but are folded, spliced, cut, or fused into new mixtures in a way that depends on local conditions almost as much as upon their own structure. Diseases as different as diabetes and prostate cancer may arise from damage in the same segment of DNA, while others such as breast cancer emerge from errors in several different genes. Most of the double helix is switched off the majority of the time, African genes are, on average, more active than are those of Europeans and life has begun to look far more complicated than any molecular biologist had feared.

Evolutionists are not in the least surprised. They were baffled at some of the decisions made by those who ran the Genome Project. Like Vesalius, James Watson and his colleagues had a Platonic view of existence. Every heart and every human was built on the same plan and to understand one was to understand them all. The first DNA sequencers outPlato-ed Plato for they a.s.sumed not just that the essence of humankind could be found within a single person, but that this Mr Average was, in the interests of political correctness, best st.i.tched together from bits of double helix taken from random donors across the globe.

That was a big mistake. The Platonic approach ignores the vital truth that evolution is a comparative science. Natural selection depends on inherited differences. To understand the past biology needs not just a single genome but many. To map variation from person to person, from place to place, or from species to species shows how, when and where evolution has been at work. So central is diversity to the idea of descent with modification that the first two chapters of The Origin The Origin are devoted to the nature and extent of variability in the bodies and habits of plants and animals. Now, genetics has begun to tell the tale in the language of DNA. are devoted to the nature and extent of variability in the bodies and habits of plants and animals. Now, genetics has begun to tell the tale in the language of DNA.

James Watson's auto-icon disclosed no more than half his secrets for it contained just one of the two versions of the double helix present in each cell. His rival in the race to decipher the secrets of life, the biologist and businessman Craig Venter, was less reticent. He read off both his copies, that received from his father and that from his mother. Venter was happy to reveal its contents: his father died young of a heart attack, and he has himself been bequeathed a variant that predisposes to the disease. He has also inherited genes supposed to increase the wish to seek novelty, to be active in the evening rather than early in the day and to have wet rather than dry ear wax.

Whatever Venter's intimate chemistry says about his personality, his bed-time or the exudations of his auditory ca.n.a.l, it has a message for us all for it gave the first hint of the true level of human diversity. Both his parents are white Europeans (and hence represent just a small sample of mankind) but their DNA is distinct at around one site in two hundred along the entire chain - which adds up to tens of millions of differences between them.

On the global scale, hundreds of millions of sites in the inherited alphabet vary from person to person and the 'Thousand Genomes Project', now well under way, has set out to fund out just how many there might be. Unlike its predecessors it will search out rare variants, those carried by fewer than one person in a hundred and present in vast abundance - and given the advances of technology, the project may cost little more than fifty million dollars. Already we know that each of the twenty-three human chromosomes - the physical location of the genes - has millions of single-letter changes aligned along it. The variable sites are so tightly packed together that, over short lengths of the double helix, they almost never separate when the molecule is cut, spliced and reordered, as it always is when sperm or egg is formed. Such long blocks represent sets of chemical letters that travel down the generations together. Rather like surnames, they are excellent clues of relatedness.

In addition to its single-letter changes, the double helix is marked by duplications of certain pieces and deletions of others. The order of its letters may also be reversed, and great stretches can hop to a new place. A study of three hundred whole genomes has already revealed a thousand and more such differences in the numbers of particular DNA sequences. Some genes are arranged in families - groups of similar structures that descend from a common ancestor and have taken up a series of related jobs. The biggest has eight hundred members. It helps build the senses of taste and smell. Its elements vary in number from person to person and some lucky individuals have fifty more copies of a certain scent receptor than do others.

Most such changes involve fewer than ten letters, but some are a million base-pairs from end to end. A few people may, because of the gains and losses, have millions more DNA bases and thousands more genes than do others and the potential variation in dose from person to person represents more than the length of the largest human chromosome. Even so, some of the repeated segments have just the same structure in humans as in the coelacanth, which split apart four hundred million years ago.

DNA is a labile and uncertain molecule. A multiplied sequence often makes mistakes as egg or sperm are formed, to produce longer or shorter versions of what went before. Some bits move or multiply at a rate of one in a hundred each generation rather than the one in a million once a.s.sumed to be typical. Age changes us and the double helix is reordered, duplicated and deleted as the years go by (which means that the offspring of older parents inherit more mutations than do those of young).

Variability beneath the skin is far more extensive than Darwin had ever imagined. Biologists have long known that, with the exception of identical twins, everyone in the world is distinct from everyone else, and from all those who have ever lived, or ever will. That claim is too modest. In fact, every sperm and every egg ever made by all the billions of men and women who have walked the Earth since our species began is unique; a figure unimaginable before the days of molecular biology.

Such variety links individuals, families and peoples into a shared network of descent. It shows how man is related to chimpanzees, gorillas, orangs and macaques, and for that matter to plants and to bacteria. Evolution - like astronomy - has always looked at the past through the eyes of the present but its new technology - like the star-gazers' development of giant telescopes - means that it can now see far further and deeper into the universe of life than once it could.

Even so, biology is not like astronomy. The images that flood from its machines are often blurred and ambivalent. Many statements about ancestry are filled with unproven, and often unstated, a.s.sumptions about the rate of change in DNA, the size of ancient populations and the effect - or supposed lack of effect - of mutations on the well-being of those who bear them. The information in the genome is almost limitless, but at present its language remains ambiguous.

Fortunately, the Earth has some better witnesses to years gone by. Like the remnants of stellar rocks that sometimes strike our planet, they are silent, shattered and few in number but at least they give direct evidence of how the past unfolded. Darwin was well aware of the importance of the fossil record to his case. One page in six of The Origin The Origin is devoted to the relics of the rocks, to the record's imperfections and to the central role it plays as proof of the fact of change. In 1871, no human fossils (with the exception of a skull from Germany now known to come from a Neanderthal) had been recognised. Things have much improved and the primate record is far more complete than it was even a few decades ago. The tale it tells is still fragmented and uncertain, but what it says fits remarkably well with the history revealed by the double helix. is devoted to the relics of the rocks, to the record's imperfections and to the central role it plays as proof of the fact of change. In 1871, no human fossils (with the exception of a skull from Germany now known to come from a Neanderthal) had been recognised. Things have much improved and the primate record is far more complete than it was even a few decades ago. The tale it tells is still fragmented and uncertain, but what it says fits remarkably well with the history revealed by the double helix.

In the Miocene epoch - from around twenty-three million to five million years ago - the Earth was a true Planet of the Apes. Primates were all over the place, with a hundred or more distinct species of ape, in Africa, in Asia and in Europe. They lived in woodlands, plains, forests and swamps. Some were no bigger than a cat and others larger than a gorilla. For much of the time their capital was in Europe and many of our predecessors have laid their bones there. Then the animals moved on, to set up shop in Africa. A ten-million-year-old fossil from Kenya may be the common ancestor of men, chimps and gorillas. If so, it confirms Darwin's speculation that it was more probable 'that our early progenitors lived on the African continent than elsewhere'. He did not, of course, know that continents had broken up and drifted across the world, and that Africa itself did not exist in the earliest days of the evolution of our line.

One day almost all the players in that ancient drama left the stage. The apogee of the apes was over and their long twilight - now fast turning into night - had begun. The sun began to set on their family well before humans appeared, but, once they did, their nemesis was a.s.sured.

Lucy, the famous fossil of Australopithecus afarensis Australopithecus afarensis, was a creature quite human in appearance, lightly built and little more than a metre tall, with relatively long legs and small teeth. She belonged to a group who lived between three and four million years before the present. Others among her kin left footprints in Tanzanian volcanic ash as proof that they walked upright at a time when their brains were but a third the size of our own. The males were considerably larger than the females. h.o.m.o habilis - h.o.m.o habilis - 'handy man' - lived in South and East Africa for about a million years from two and a half million years ago. It had long arms, brow ridges and a larger brain than Lucy, and was quite good at making tools. Similar individuals were found in Africa, and perhaps in Georgia. 'handy man' - lived in South and East Africa for about a million years from two and a half million years ago. It had long arms, brow ridges and a larger brain than Lucy, and was quite good at making tools. Similar individuals were found in Africa, and perhaps in Georgia.

h.o.m.o erectus the upright human, the next fossil claimed as a direct (or almost direct) human ancestor, emerged around 1.8 million years ago, and may have split into two species in its homelands in Africa and Asia. Some individuals had brains as large as our own and lived as far north as the South of France. A rather younger European arrived around 1.2 million years before the present, and left a few of his bones in the caves of the Sierra de Atapuerca in northern Spain. That ancient Spaniard has been christened h.o.m.o antecessor h.o.m.o antecessor, and might be the common ancestor of ourselves and the Neanderthals. A later European from around half a million years ago, Heidelberg Man, may have been an antecedent of the Neanderthals rather than ourselves. He too first appeared in Africa. Many - perhaps too many - more supposed members of our close family have been named as distinct species, and the human pedigree has begun to look more like a bush than a tree. As a result, direct lines of descent have become harder to trace than once they were.

For most of history, our ancestors shared their home with several related species that were much closer to themselves than the chimpanzee is to us. Those days have gone, and nearly all members of man's ancient household have left no issue today.

The Neanderthals were once our most immediate kin. They lived in Europe and the Middle East from around a quarter of a million years ago to about thirty thousand. They had bigger skulls - and, perhaps, bigger brains - than modern humans (although they were also beefier in general). They trapped animals in pits, and may have been cannibals (although another view of the carved bones of their fellows is that they represent a ritual burial). Neanderthals lived in small groups in an icy Europe for far longer than our own species has existed, and then disappeared. Like many other apes, they went quickly. Perhaps a cold snap defeated them, for a remnant hung on in the warmth of southern Spain until well after the moderns arrived. The victors had better clothes, which allowed the tropical ape that they were - and we are - to survive in a climate that killed off an animal more used to bad weather but less well clad. Perhaps h.o.m.o sapiens h.o.m.o sapiens murdered the Neanderthals or starved them out, but we do not know. s.e.x was not on the agenda, for fossil DNA from a Croatian specimen shows that they were quite distinct from our direct ancestors. In addition, today's Europeans and Middle Easterners retain no ancient lineages that might have come from an extinct relative. DNA suggests that the Neanderthals' last common ancestor with modern humans lived in Africa more than six hundred thousand years ago, long before murdered the Neanderthals or starved them out, but we do not know. s.e.x was not on the agenda, for fossil DNA from a Croatian specimen shows that they were quite distinct from our direct ancestors. In addition, today's Europeans and Middle Easterners retain no ancient lineages that might have come from an extinct relative. DNA suggests that the Neanderthals' last common ancestor with modern humans lived in Africa more than six hundred thousand years ago, long before h.o.m.o sapiens h.o.m.o sapiens emerged. emerged.

Soon after the loss of his cousin, that species began to spread across the world. Modern humans filled the whole habitable globe no more than a thousand or so years before the present, when at last men and women reached New Zealand and Hawaii. Their ancient journeys can still be read in DNA. The double helix reveals a clear split between Africa and everywhere else, a legacy of the small group of migrants who first stepped out of our native continent into an uninhabited world, together with a second and more ancient split within Africa that separates the Khoi-San - the Bushmen - from all others. Other great genetic trends, such as those across the New World and the Pacific, track the last migrations into a deserted landscape.

Once, it seemed that modern Europe had a more complicated history than did most of the globe, with several waves of migration superimposed on each other. The genes of local hunters, who arrived long ago, were - perhaps - diluted by those of the first farmers who spread, just a few thousand years before the present, from a population expl