The man who dared to climb the family tree

One morning in 1858 Charles Darwin picked up his mail and discovered a letter from Alfred Russel Wallace. Darwin had spent 20 years working out evidence to support his theory of natural selection, secure in the knowledge that the theory was too radical and the details too arcane for anyone else to have thought out. He could have published all or part of his work at almost any point; his closest scientific friends often urged him to do so. But he kept silent because he dreaded the consequences: Publication would invite public condemnation likely to make Rome's reception of Galileo look friendly. He didn't think that he could bear the notoriety.

Then came the paper from Wallace, laying out the theory of natural selection in words that could very nearly have been Darwin's own.

Janet Browne could not have chosen a more dramatic incident to begin the second book of her riveting two-volume biography of Darwin. In the entire range of intellectual history, there is not a moment that tops the Darwin-Wallace collision for sheer human drama. With Wallace somewhere in the remote rain forest of southeast Asia – weeks away by the fastest steamers – no one would ever have known if Darwin had "lost" that manuscript. It is unlikely that he even considered such a course.

Over the course of these two volumes, we come to understand the man's character intimately. Partly because Browne has waded through endless bundles of family letters that have sat unread since the original recipients tied them with silk ribbons. Partly because Browne, a British professor of the history of biology, understands Darwin's world. But mostly because she is a master of the art of biography.

Darwin was bound to publish Wallace's paper. The great question was, would he publish his own? His agonized decision came down to deciding which he dreaded more: facing the public scorn that evolution aroused in Victorian England, or allowing credit for the theory that had been his life's work to go to someone else. At this point the story becomes weirdly modern.

Darwin inhabited an old-fashioned world that is very foreign to us. He got the chance to explore not because he was a qualified scientist, but because he was a conversable gentleman from the right sort of family. He never held a paying job. Some English gentlemen did work, but it was more respectable to settle in a big country house and live on inherited money. Charles married his first cousin, and each of them inherited part of grandpapa Wedgewood's china fortune.

But the most startlingly unmodern thing about Darwin was, in the words of his son Francis, "the curious fact that he who has altered the face of Biological Science, and is in this respect the chief of the moderns, should have written and worked in so essentially a non-modern spirit and manner."

During the course of Darwin's career, scientific instrument makers began to produce equipment that improved, for example, the control of moisture or light available to growing plants. Yet Darwin continued to potter about the kitchen, rigging equipment with material borrowed from his wife's sewing basket. His hopelessly old-fashioned methods produced cutting-edge science right up to the year he died.

When it came to handling the publicity for "The Origin of Species," by contrast, the slickest Madison Avenue PR firm could not have been more cutting edge than Darwin and his tailcoated friends. With finesse a modern publisher must envy, Darwin softened up potential reviewers by sending signed copies with admiring, personal notes to nearly every eminent scientist in Europe and America. (Full disclosure: I have never received a personal letter from either Janet Browne or Charles Darwin.)

As often as possible, however, Darwin's scientific friends avoided any risk of getting a bad review by writing the reviews themselves, an easier trick in the days when reviews ran anonymously. They also set about making certain that reviews would run in all the right places.

In the cozy Victorian world of British science, becoming a scientist in the first place indicated that one had come from a financially comfortable background. The eminent men of science and of letters had gone to the same schools and belonged to the same clubs, clubs whose more tedious members could tell you precisely which scientist was the cousin of which editor on precisely which side of the family.

This look inside the workings of Victorian science is among the great fascinations of Browne's book. Darwin's friends needed a compelling explication of evolution to move science forward. The minute Wallace's paper arrived, they pushed hard for Darwin to publish. No sooner had the "Origin" gone to the typesetter, than Darwin and his friends set about ensuring that not only the book but the theory itself would succeed. Every stop was pulled in the battle against creationism.

Finally, in a carefully orchestrated publicity maneuver on behalf of evolutionary theory, two dukes, one earl, the American ambassador, the president of the Royal Society, and four eminent scientists – Wallace, Hooker, Lubbock, and Huxley – carried the old atheist's coffin to a grave in Westminster Abbey. But not even death could free Darwin from controversy.

• Diana Muir is the author of 'Reflections in Bullough's Pond: Economy and Ecosystem in New England' (University Press of New England).