Biologist Theodosious Dhobzansky once said, "Nothing in biology makes sense except in light of evolution." While the physical sciences can point to Newtonian mechanics, relativity and quantum mechanics as their grand overarching theories, the life sciences, arguably, just have evolution. And for most of us evolution means one man: Charles Darwin.

But who was this man who set a revolution in motion? If anyone knows, it is Professor Janet Browne, a historian at the Wellcome Trust Centre for the History of Medicine at University College London, the second volume of whose acclaimed biography of Darwin was published in October 2002.

"He's not an easy man to characterise," admits Professor Browne, "and that’s partly why I’ve written the book. He’s complex, and many layered. He’s not presenting different faces to different people – he’s not duplicitous in that regard, but he is a complex man." The second volume of her story picks up in 1856, with Darwin established as a ‘gentleman scientist’ at Down House in Kent, where he was to spend the rest of his life.

His relocation to the seclusion of Down House has helped foster a view of Darwin as a recluse. Professor Browne argues this is too narrow a view. "On the surface he’s shy, modest, retiring. But he was jolly, people don’t really appreciate how friendly and jolly he was: a pleasant-natured man, good humoured. And underneath there’s this extraordinary depth of feeling for the natural world and investigative power that he didn't really let show except in the written work. There’s another man that you have to go beneath to try and find. The one who writes the books and who has astonishing ideas."

Darwin’s astonishing idea was, of course, natural selection - that living things had been shaped by the world they were living in, occasional variants being selected for survival, leading to the highly adapted forms of life seen today. It was heady stuff for a Victorian audience - particularly the implication that humans, far from being created in God’s image, were little more than hairless apes. Darwin set out his ideas in ‘On the Origin of Species’ in 1859.

Evolution in the air
Evolutionary theory may have crystallised around Darwin, but he was not ploughing a solitary furrow. Evolutionary thinking was in the air. Indeed, Darwin was horrified to discover that many of his key ideas had independently occurred to another naturalist, Alfred Russel Wallace, who wrote to Darwin outlining a theory alarmingly like his own. Darwin had been gestating his theory of natural selection for years but had published nothing. Now it looked as if he would be pre-empted.

Unsure what to do, he sought advice from his friends, Joseph Hooker (a botanist at Kew) and Sir Charles Lyell (an eminent geologist). Not for the first or last time, Darwin’s friends in high places came to the rescue. Their solution was for Darwin to produce an outline of his theory, which he could publish alongside Wallace’s. The joint publication provided a compromise Darwin could live with. "It did seem to him like a very gentlemanly, reasonable solution."

The evolutionary thinking of both Wallace and Darwin was very much in tune with the age's preoccupation with ‘progress’. Human life was seen as the inexorable rise from a barbaric past to higher civilisation (Victorian gentleman being pretty much top of the tree). In history, politics and economics, even novels, writing was permeated by the onward march to better things.

Darwin also picked up ideas from his own background, in competition for example. "He gets most of his understanding of that from his background as part of a manufacturing elite. He’s very aware in his own family line of the Wedgwood potteries and the success of competition and entrepreneurial work and capitalism. So he’s not an economical thinker but he’s aware of it; he grows up in that sort of environment."

In natural history, too, Darwin was not alone. Robert Chambers, a publisher from Edinburgh, had caused ripples with his anonymous work, ‘Vestiges of the Natural History of Creation’.

"Every element of his theory and much of the evidence he draws upon for his theory could be found in the surrounding science and social life of the time," points out Professor Browne. "It’s not all that unreasonable that somebody like Wallace would come up with the same idea. But even before that there was Robert Chambers, whose theory is not at all like Darwin’s but he's still proposing an evolutionary scheme, as did someone who hardly ever gets mentioned, Herbert Spencer. It’s Spencer who coins the phrase ‘survival of the fittest’ that Darwin then pops into his book a bit later in the 1860s."

So if Darwin was drawing upon public knowledge, and his ideas were not so different from Wallace’s, why was it a Darwinian revolution? "It wouldn't have taken the shape it did without Darwin, there’s no question about that. And the shape is interesting."

Darwin’s real contribution, suggests Professor Browne, was The Origin of Species. "Darwin’s real achievement, surely, is just writing that book, ‘The Origin of Species’, and bringing it to the public."

Timing was again important. Publication coincided with a period when books were beginning to be produced and distributed much more widely. Review journals were springing up. Publishing was a growth industry. Darwin’s ideas were disseminated far more successfully than they would have been a few years earlier. "I think it’s the book, it’s ‘The Origin of Species’, as a publishing event, that actually makes for the Darwinian revolution."

The Origin of Species made an immediate impact, but it was by no means inevitable that Darwin's ideas would be accepted. The next few decades witnessed a fierce struggle as Darwin and his intellectual allies fought to keep the fledgling theory alive, under attack from other scientists, powerful religious forces and social commentators alarmed at the theory’s implications. One of Darwin’s closest friends, the pugnacious T H Huxley, is often credited with leading the Darwinian charge. Yet, suggests Professor Browne, Darwin’s own role has been underestimated.

"I’m very keen to show that he was a publicist but of a different kind to the kind we expect. He wasn’t the front man like Huxley going out on public platforms but he was a very skilled strategist behind the scenes." His chosen weapon was the pen. From his base at Down House he sent out a barrage of carefully constructed letters to people of influence, sending out copies of the book to everyone he thought might aid his cause. "It sounds relatively innocuous but he was writing many letters every week to all kinds of well-known individuals, some of whom he knew, some of whom he didn’t, asking them to read his book, if not favourably then at least with an open mind. We’re talking a couple of thousand letters in the first year after publication. That’s a lot of effort."

The evolution of ideas
As Huxley’s enthusiastic support illustrates, Darwin’s theory rapidly became public property, adopted, challenged, interpreted, added to. Darwin himself modified his views over the course of many editions he produced, becoming much more open to environmental influences on heredity in later life.

The development of the theory fires Professor Browne's imagination. "There’s scientific transformation going on and Darwin is just one figure in the middle of it. He’s pulling lots of strings but it’s not just him alone. I find that absolutely intriguing. And you can apply that to the 20th and 21st century - how knowledge gets made. It’s the wonderful thing about science. It’s the relationship between one mind and the community."

Back at Down House, Darwin watched his theory growing and spreading. He became a celebrity. People would call in unannounced, or simply to gawk. Time and again, Darwin fell back on his trusty excuse - his ill-health.

The exact nature of his illness has long perplexed historians - more than 50 theories have been proposed over the years. He complained of severe stomach pains and vomiting for much of his adult life. At times, it completely incapacitated him. Yet it is equally true that he took full advantage, organising the Down House schedule around himself, using his sickness to avoid trips or visits he did not wish to make, or to curtail meetings with visitors. He preferred the sanctuary of his study.

Yet it would be misleading to describe him as reclusive. He may not have sought excitement in his life, but he undoubtedly liked good company. He was a frequent visitor to spas, where he went to recuperate when his illness became too much, and enjoyed lively and intelligent conversation with fellow invalids. In many other ways his life offers contradictions. He had a deep-grained sense of duty, but certainly manipulated his illness for his own benefits. He was an instinctive Liberal, but deeply conservative. He was generous but very careful with money. He was an innovative thinker and could overthrow conventional thinking, but his views on the social order were those of a typical Victorian gentleman.

Darwin set great store by family life. The death of his daughter had a profound effect upon him, particularly in his religious views. He simply could not countenance the fact that a god had intended this to happen. In fact, says Professor Browne, his religious views are hard to pin down. "He’s ambiguous all the time. He didn’t like people asking him what he believed." There are signs that he had a faith of sorts when he was writing Origin, but in later life when his belief is very remote. "When people contest him, saying ‘you’re an atheist’, he says ‘no, I’m not’. When he’s in his late 60s, early 70s he really is pretty much agnostic - Huxley invents that word and Darwin is very glad to have a word that explains what he believes."

He was devoted to his wife, Emma, who did retain strong religious beliefs. But she seems not to have attempted to dissuade him from his free thinking; and he was very careful about how he portrayed his ideas. "He is sensitive to her views. But she was tolerant and supportive. Her devoutness was tempered with good humour and a loving relationship. She wasn’t a theological policeman and didn’t make him worried about what he was doing. That’s one of the reasons he drains all his manuscripts of God and mankind; he doesn’t talk about mankind in ‘The Origin of Species’."

So the real Darwin appears. Able to put forward views he knew would be deeply troubling: putting them forward nevertheless, but sensitive to how they would be received. Driven by a sense of duty, which encompassed his personal actions but also his devotion to the scientific truth. A man who had an impact all over the world, but who never lost sight of those closest to him. "It’s obvious that people loved him very much. His family loved him. All Victorian children were supposed to love their parents, but I think it’s genuine. But the love his friends feel for him is very marked. Huxley and Hooker and Lyell truly thought of him as a brother and someone they were very fond of. To generate those kinds of feelings as well as a book like Origin is quite remarkable."

See also

• Professor Janet Browne at the Wellcome Trust Centre for the History of Medicine at University College London: Research interests