Singular life of a jungle philosopher

Alfred Russel Wallace is a familiar figure as Darwin's doppelgänger , but they can also be seen as two characters, each with his own preoccupations, whose paths crossed at one critical point in the 1850s. We know Darwin well from Adrian Desmond and James Moore's rich 1991 biography and Janet Browne's excellent first part that appeared in 1995. Peter Raby, author of Bright Paradise : Victorian Scientific Travellers , now offers Wallace's life, from his childhood in genteel poverty through a youth of self-improvement and on after his scientific adventures collecting zoological specimens in Amazonia and the Malay Archipelago.

Wallace sent his conjecture about the origin of species from his hut in the Moluccas to the other person in the world who, unknown to him, had secretly come to the same conclusion. They shared the credit; Darwin worked up and published his full theory, and Wallace then spent the remaining 50 years of his life developing his own "Darwinism" in an opposite direction from his increasingly uneasy friend. He wrote with radical idealism about moral and social issues, and reached audiences whom Darwin never addressed. In his last years he was widely admired, but after the first world war, his Utopian ideas were forgotten and he has often been pictured since as a humble genius eclipsed by his wealthy rival for the glory of the great discovery.

Raby shows that "Wallace was not a victim and did not see himself as a victim". He portrays this brilliant, wilful and unworldly figure in all his engaging idiosyncrasy. He makes economic use of Wallace's prolific writings, sketching in the social background, and drawing on recent scholarship to explain elements of Wallace's views. It quickly becomes clear, though, that the many dramas of Wallace's life stemmed from his thinking as he reached out for ideas against the social and scientific flow. As the years passed, he put Owenite ideals together with mesmerism, plant and animal geography, Robert Chambers and Herbert Spencer's evolutionary progress, Thomas Malthus's population checks, natural selection and a faith in the reality of paranormal phenomena, to form a world view that was entirely his own. It is one of the many wonders of the late Victorian age, as interesting to explore as any other approaches that have proved more acceptable to subsequent thinking.

Wallace developed his understanding of living species "in time and space" as he scoured Brazilian and Malaysian forests for specimens to sell to museums and collectors. He kept 3,000 bird skins and 20,000 insects for his own work, and used his findings in his two main scientific books, The Geographical Distribution of Animals and Island Life . But he depended on the market for his livelihood. It was a bizarre high Victorian business. How was his science influenced by this strange trade as he netted iridescent butterflies, pinned antlered beetles, skinned and skeletonised orang-utans, and shot birds of paradise? He learnt an early lesson about natural populations and their boundaries when he gathered from Amazon Indians that three kinds of trumpeter bird he wanted each lived in their own area of forest separated by the great river. How did he work as a collector, field naturalist and zoological philosopher, combining the hunt, close observation and wide-ranging views? How did he trace "Wallace's line", the great zoological discontinuity across the Malay Archipelago that is now explained by the geology of plate tectonics?

Raby shows how Wallace took Darwinism in his own direction with a special emphasis on progress and spirituality. He describes a seance witnessed by the Harvard philosopher William James. A spiritual apparition approached Wallace, who thought at first it might be Darwin. Disappointingly, it wasn't. Was it perhaps cousin Algernon? The figure nodded enthusiastically. It is an arresting moment in the book. Wallace was a powerful and coherent thinker on many issues, but how did his scientific, moral and spiritual ideas really fit together?

Raby tells Wallace's life story mainly through Wallace's own eyes, and at certain key points the reader is left wondering what his arguments meant to others. Some respectable people with orthodox opinions honoured him for his scientific achievements and dismissed his radical politics and spiritualism as aberrations. But many others, a whole popular readership in fact, appreciated his writings as the highly distinctive contributions of a leading scientist to debates on moral and social themes. Wallace seems to have cared more for his second audience, perhaps because he felt more at home in their wider, harder world. He needs to be understood as he lived, a remarkable figure in these two communities.

Randal Keynes is author of Annie's Box : Charles Darwin, His Daughter and Human Evolution .