How Darwin won the evolution race

It's 150 years since Darwin made one of the the most significant breakthroughs in scientific history - the theory of natural selection. But if it hadn't been for a young ornithologist on the other side of the world, his seminal work might never have appeared. Robin McKie tells the extraordinary story behind The Origin of Species

British Naturalist Charles Robert Darwin. Photograph: Rex Features

In early 1858, on Ternate in Malaysia, a young specimen collector was tracking the island's elusive birds of paradise when he was struck by malaria. 'Every day, during the cold and succeeding hot fits, I had to lie down during which time I had nothing to do but to think over any subjects then particularly interesting me,' he later recalled.

Thoughts of money or women might have filled lesser heads. Alfred Russel Wallace was made of different stuff, however. He began thinking about disease and famine; about how they kept human populations in check; and about recent discoveries indicating that the earth's age was vast. How might these waves of death, repeated over aeons, influence the make-up of different species, he wondered?

Then the fever subsided - and inspiration struck. Fittest variations will survive longest and will eventually evolve into new species, he realised. Thus the theory of natural selection appeared, fever-like, in the mind of one of our greatest naturalists. Wallace wrote up his ideas and sent them to Charles Darwin, already a naturalist of some reputation. His paper arrived on 18 June, 1858 - 150 years ago last week - at Darwin's estate in Downe, in Kent.

Darwin, in his own words, was 'smashed'. For two decades he had been working on the same idea and now someone else might get the credit for what was later to be described, by palaeontologist Stephen Jay Gould, as 'the greatest ideological revolution in the history of science' or in the words of Richard Dawkins, 'the most important idea to occur to a human mind.' In anguish Darwin wrote to his friends, the botanist Joseph Hooker and the geologist Charles Lyell. What followed has become the stuff of scientific legend.

In order to preserve Darwin's claim on natural selection Hooker and Lyell arranged for a joint reading of both men's works at the Linnean Society in Burlington House, Piccadilly. On 1 July in a room that is now part of the Royal Academy, society members were summoned to hear the news of a theory that has gone on to cause more offence and trouble to our species than any other in our history. Exactly 150 years ago next week, a notion, more radical even than Marx's, was set loose on the world - though it certainly did not seem that way at the time.

For a start, Darwin and Wallace did not give eloquent lectures to a cheering mass of Linnean Society members who realised God was dead, as is often suggested. Neither scientist was present: Wallace was still in Malaysia while Darwin was at home grieving with his wife, Emma, over the death, on 28 June from scarlet fever, of their 19-month-old son, Charles.

Then there was the audience. It was made up of gentleman amateurs. For several hours they were bombarded with items of society business followed by readings of Darwin and Wallace's notebooks, papers and letters. At the end, members walked out 'not so much stunned by new ideas as overwhelmed by the amount of information loaded upon on them,' said historian JWT Moody in a 1986 study of the meeting. Bored silence greeted the news that humanity had been deposed from the centre of creation.

Months later, the intellectual penny had still not dropped. The Linnean society's president Thomas Bell, writing in his review of 1858, concluded the year had not been marked by 'any of those striking discoveries which at once revolutionise the department of science' - presumably, the dethroning of God being insufficiently revolutionary for his liking.

Nevertheless the fuse had been lit. 'Wallace's letter gave Darwin a good kick up the backside,' says the geneticist Steve Jones. 'He had prevaricated for 20 years and would have done so for another 20 if he hadn't realised someone else was on the trail.' The summer of 1858 changed everything for Darwin. Although by no means an arrogant man, he knew his worth. He was already a Royal Society Gold Medal winner and was not going to be robbed by a whippersnapper specimen collector in Malaysia. So he sat down, with a board across his knee, on the only chair in his house that could accommodate his long legs, and wrote up the research he had been carrying out for the past 20 years.

The end result was On the Origin of Species by Means of Natural Selection, whose 150th anniversary will be celebrated next year along with the 200th anniversary of Darwin's birth. Remarkably, it is the only major scientific treatise to have been written, deliberately, as a piece of popular writing, a book whose interlacing story lines have been compared with those of George Eliot or Charles Dickens and which is peppered with richly inventive metaphor. 'Darwin was creating a lasting work of art,' as Darwin's biographer Janet Browne puts it.

This praise is echoed by Dawkins whose Channel 4 series Dawkins on Darwin will be screened this August. 'When you read The Origin of Species, you get a real feeling that Darwin was very keen to be understood. He did not want merely to persuade fellow scientists, he wanted to show to the public the truth of his ideas. He took great pains with it, which is why it is such a convincing book. Its sentences are perhaps a bit long-winded by modern standards, but for its time it must have been an easily understood work.'

This accessibility ensured natural selection came to the public's attention in a much more vivid form than might otherwise have been expected and hastened those anguished and outraged responses that Darwin had anticipated. 'Utterly false and grievously mischievous,' said Darwin's old teacher, Adam Sedgwick, in a letter to his former pupil. Darwin's supporters - Hooker, Lyell and Thomas Huxley - rallied to his defence, beginning a battle that culminated in the famous debate between Huxley and Bishop Wilberforce at the British Association for the Advancement of Science in Oxford, in June 1860. Huxley is popularly credited with defeating Wilberforce - at an institution where two-thirds of graduates took holy orders. Not a bad show, though the decisive nature of Huxley's 'victory' is now questioned by many historians. It was more a score draw, they reckon. On the other hand, it is clear that change was in the air and the publication of The Origin of Species accelerated this transformation. The Church, until then the nation's authority about the natural world, was losing ground and science was taking over.

'Over the following decades, Darwin's defenders came to occupy influential niches in British and American intellectual life,' notes Browne. 'Toward the end they were everywhere, in the Houses of Parliament, the Anglican Church, the universities, government offices, colonial service, the aristocracy, the navy, the law and medical practice; in Britain and overseas.' These men ensured natural selection endured and saw to it that Darwin received a Westminster Abbey burial in 1882 - not bad for an avowed agnostic.

Darwin remains venerated to this day, his features appearing on the current £10 note. By contrast Wallace has been forgotten. He was happy to let Darwin and his friends promote natural selection. 'This assures me the acquaintance and assistance of eminent men on my return home,' he told his mother. A general suspicion remains that he got a raw deal, however. Self-educated and from a humble background, Wallace had none of the privileges accorded to university-educated Darwin, whose father was a prosperous doctor. He had had to make his way as an apprentice carpenter and then a trainee surveyor, before turning himself into a distinguished naturalist. He was also an early socialist, a supporter of women's rights, a backer of the land reform movement and a consummately skilful writer. Joseph Conrad kept a copy of The Malay Archipelago - Wallace's account of his eight years in the region - on his bedside table and drew on it for his own books, most notably Lord Jim

But Wallace was also blighted both in luck and in character. His first great specimen-gathering expedition - to the Amazon - ended in disaster when the ship returning him to Britain caught fire and sank, taking with it thousands of specimens and his hopes of an assured income. The collector survived with only a couple of notebooks and an indignant parrot.

And Wallace was impetuous. While Darwin fully understood the implications of his theory, holding back publication because he knew he would upset believers, including his wife, Wallace plunged in, happy to upset society. He didn't give a damn, said Jonathan Rosen, in an essay on Wallace in the New Yorker last year. 'This utter independence from public opinion is one of several reasons that he has all but vanished from popular consciousness.'

In addition, Wallace believed in spiritualism (which Darwin and his friends detested) and later campaigned against vaccination. 'Wallace was an admirable man and was almost saintly in his treatment of others,' says David Attenborough. 'However, as a scientist, he was no match for Darwin. Wallace came up with the idea of natural selection in a couple of weeks in a malarial fever. Darwin not only worked out the theory, he amassed swathes of information to support it.'

This point is backed by historian Jim Endersby. 'Natural selection was a brilliant idea but it was the weight of evidence, provided by Darwin, that made it credible. That is why we remember Darwin as its principal author.' On his round-the-world voyage on the Beagle, between 1831 and 1836, he had filled countless notebooks with observations, particularly those of the closely related animals he saw on the different islands of the Galapagos. And then, in his vast garden at Downe, Darwin had crossbred orchids, grown passionflowers and on one occasion played a bassoon to earthworms to test their response to vibrations. He collected masses of data about plant and animal breeding to support his arguments in The Origin of Species. Wallace could provide nothing like this.

This has not stopped accusations that Darwin and his supporters used some very dirty tricks indeed to scupper Wallace. According to these ideas, Darwin received Wallace's paper from Ternate several weeks earlier than he later claimed, filched its contents and then used them as his own in The Origin of Species. This argument is outlined in two American books - by Arnold Brackman and by John Langdon Brooks - that were published 20 years ago and depict Darwin as an unscrupulous opportunist and intellectual thief. Neither book provides anything like a convincing case, however, and the vast majority of academics have since concluded their claims are neither fair nor credible.

As Wallace's own biographer Peter Raby concludes: 'Never has an intriguing theory been built on slenderer evidence. As for the human factor, there is nothing in Darwin's life to suggest that he was capable of such massive intellectual dishonesty, even if he was not especially generous in acknowledging his sources and debts.'

Indeed, historians argue that had it not been for Darwin, the idea of natural selection would have suffered grievously. If he had not been the first to develop natural selection, and Wallace had been the one to get the kudos and attention, the theory would have made a very different impact. 'In the end, Wallace came to believe evolution was sometimes guided by a higher power,' adds Endersby, who has edited the forthcoming Cambridge University Press edition of The Origin of Species. 'He thought natural selection could not account for the nature of the human mind and claimed humanity was affected by forces that took it outside the animal kingdom.'

This is perilously close to the idea of Intelligent Design, the notion - put forward by modern creationists - that a deity had a hand in directing the course of evolution. By contrast, Darwin's vision was austere and indicated humanity as a mere 'twig on the enormously arborescent bush of life which, if replanted from seed, would almost surely not grow this twig again', as Stephen Jay Gould describes it. According to Darwin, there are no get-out clauses for humans. We are as bound to the laws of natural selection as a bacterium or a tortoise.

The roots of this unforgiving doctrine have a very human face, however. Darwin meshed his life and career tightly together. He was a family man to his core and while he was grief-stricken by the death of baby Charles in 1858, he had been left utterly shattered by the death from tuberculosis of his 10-year-old daughter, Annie, in 1851, as his great-great grandson, Randal Keynes points out in his book Annie's Box: Charles Darwin, his daughter and human evolution. Mustard poultices, brandy, chloride of lime and ammonia were all that medicine could then offer Annie when she started to sicken. None had any effect on her worsening bouts of vomiting and delirium until Annie 'expired without a sigh' on 23 April 1851, Darwin recalled. 'We have lost the joy of the household and the solace of our old age.'

Keynes argues persuasively that Annie's death had a considerable impact on Darwin's thinking. 'In her last days, he had watched as her face was changed beyond recognition by the emaciation of her fatal illness. You could only understand the true conditions of life if you held on to a sense of the true ruthlessness of natural forces.'

Thus Darwin's eyes had been opened to the unforgiving processes that drive evolution. 'We behold the face of nature bright with gladness,' he wrote years later. 'We do not see, or we forget, that the birds which are idly singing around us mostly live on insects or seeds, and are thus constantly destroying life, or we forget how largely these songsters, or their eggs, or their nestlings, are destroyed by birds or beasts of prey.' Or as he wrote elsewhere: 'All Nature is war.'

This pitiless vision - which stressed blind chance as the main determiner in the struggle for survival and the course of evolution - was upsetting for Victorians who put such faith in self-help and hard work. Nevertheless, this is the version of natural selection which has since been supported by a century and a half of observation and which is now accepted by virtually every scientist on earth.

It has not been a happy process, of course. Even today, natural selection holds a special status among scientific theories as being the one that it is still routinely rejected and attacked by a significant - albeit small - segment of society, mainly fundamentalist Christians and Muslims. Such individuals tend to have few views on relativity, the Big Bang, or quantum mechanics, but adamantly reject the idea that humanity is linked to the rest of the animal world and descended from ape-like ancestors.

'Twenty years ago, this was not a problem,' says Steve Jones, a professor of genetics at University College London. 'Today, I get dozens of students who ask to be excused lectures on evolution because of their religious beliefs. They even accuse me of telling lies when I say natural selection is backed by the facts. So I ask if they believe in Mendel's laws of genetics? They say yes, of course. And the existence of DNA? Again, yes. And genetic mutations? Yes. The spread of insecticide resistance? Yes. The divergence of isolated populations on islands? Yes. And do you accept that 98 per cent of DNA is shared by humans and chimps? Again yes. So what is wrong with natural selection? It's all lies, they say. It beats me, frankly.'

This dismay is shared by Dawkins. 'These people claim the world is less than 10,000 years old which is wrong by a great many orders of magnitude. Earth is several billion years old. These individuals are not just silly, they are colossally, staggeringly ignorant. I am sure sense will prevail, however.'

And Jones agrees. 'It's a passing phase. In 20 years, this nonsense will have gone.' Natural selection is simply too important for society to live without it, he argues. It is the grammar of the living world and provides biologists with the means to make sense of our planet's myriad plants and animals, a view shared by Attenborough whose entire Life on Earth programmes rests on the bed-rock of Darwinian thinking.

'Opponents say natural selection is not a theory supported by observation or experiment; that it is not based on fact; and that it cannot be proved,' Attenborough says. 'Well, no, you cannot prove the theory to people who won't believe in it any more than you can prove that the Battle of Hastings took place in 1066. However, we know the battle happened then, just as we know the course of evolution on earth unambiguously shows that Darwin was right.'

Darwin and Wallace's theory: The four key parts

· Creatures of the same species differ from each other in ways that are inherited. This is known as variation. An example is provided by the giant tortoises of the Galapagos archipelago, which Darwin studied in detail. Among those born to the same parents, some will have longer necks than others.

· More creatures in a population are born than can survive. This is the struggle for existence.

· Some creatures of the same species possess characteristics that give them a better chance of surviving and reproducing than others in that species. In the case of Galapagos tortoises, those with longer necks will be able to reach up higher to feed off plants, a useful characteristic during droughts when grass is not available to provide food. This is natural selection.

· These favoured characteristics are passed on to future generations and accumulate. Over a long period, new forms of life evolve. This is the origin of species. For the Galapagos' more arid islands, it meant the appearance of tortoises capable of stretching up to higher branches.

Chance discovery: Darwin's lucky break

Charles Darwin's name is linked irrevocably with natural selection. Yet his involvement with the theory was not preordained. He initially turned down the chance to travel on the Beagle, and only later changed his mind. In addition, there was the origin of the post he filled onboard. The position of naturalist was privately funded by its captain, Robert Fitzroy. The latter, although a gifted seaman, was a melancholy man obsessed by the suicide of his uncle, Viscount Castlereagh, a Tory politician who committed suicide by cutting his throat on 12 August 1822.

Fitzroy was convinced he had inherited the same suicidal tendencies, which might claim him at any time on the voyage. So he paid for a companion - Darwin - to help keep him from despondency on the five-year trip. Darwin recalled Fitzroy's 'low spirits, on one occasion bordering on insanity'. Thus Darwin's odyssey came about only because of one man's dread of inherited insanity. Had a senior member of the Conservative government not killed himself, his nephew would not have worried about family madness and he would not have sought a learned companion to distract him.

The history of science would have been very different. The term Darwinism would be unknown, and we would most likely speak of Wallacism today when talking about natural selection. On the other hand, Darwin's presence seems to have been beneficial. Fitzroy returned intact and was later made head of the body that was to become the Meteorological Office. (The shipping forecast area Fitzroy is named after him.) His morbid fear of suicide was not misplaced, however. In a fit of melancholy, Fitzroy killed himself - by cutting his throat - on 30 April 1865.

A brief history of evolution

What they said - about where we come from - when

Sixth century BC

The idea that species could change and evolve into other species existed before Darwin and Wallace came up with their theory of natural selection. The ancient Greek philosopher Anaximander put forward early evolutionary ideas, for example. However it was not until the end of the 18th century, with the development of the sciences of botany and geology, that the idea of evolution was debated seriously. The problem for naturalists was simple, however. If God did not create every type of living creature, how did one type of animal or plant change into another? What process drove evolution?

1800

One of the first proposed mechanisms was put forward by the French naturalist Jean-Baptiste Lamarck. He argued that characteristics acquired by an animal during its life were passed on to future generations. An animal which developed muscles or a long neck would pass these on to its offspring. The idea was the first decent shot at deriving a theory of evolution. Unfortunately for Lamarck, it has not survived the scrutiny of science. Generations of cats which have had their tails docked have not evolved into tail-less cats. Acquired characteristics are not inherited, though the idea persisted as a serious scientific concept into the 20th century.

1830-1833

Another key event in the development of a mechanism that could explain the evolution of species was the publication of the three volumes of Charles Lyell's Principles of Geology between 1830 and 1833. Lyell argued that the history of the Earth was not one of short-term violent transformations or catastrophes but one of gradual changes that took place over extremely long periods. This vision of a planet shaped by tiny alterations - caused by erosion, sediment formation, the impact of wind and other factors - operating over aeons had a profound impact on naturalists.

1858

The ideas of Wallace and Darwin were read at the Linnean Society in London. Both men had been deeply influenced by their observations of wildlife across the globe. On his round-the-world journey on the Beagle, Darwin had also carried a copy of Lyell's Principles of Geology, which provided a background to his studies of animals and plants in the Galapagos and other parts of the world. Wallace, for his part, had made his observations in the Amazon and Malayasia.

1865

The Origin of Species, published in 1859, lacked one key feature: an understanding of genetics. That knowledge was provided by Gregor Mendel in 1865 when his studies of plants led him to develop the laws of genetics. The basic unit of this process is the gene,which is the focus of the forces of natural selection. Mendel's laws were overlooked by mainstream science until the start of the 20th century, however. Only then was it possible to understand the genetic mechanisms that underpin natural selection.

1953

Francis Crick and James Watson unravel the structure - a double helix - of deoxyribonucleic acid (DNA), the material from which the genes of all living creatures, from ants to whales, is constructed. The discovery allows scientists to begin detailed studies of the impact of natural selection at a molecular level.