Charles Darwin (1809-82) will forever be linked with the theory of evolution by means of natural selection, which explains how life on Earth has developed and diversified over three billion years from the simplest single-celled organisms to the vast richness of flora and fauna we can see today.
What is less well known is that this elegant theory was also conceived by another, more obscure scientist: Alfred Russel Wallace (1823-1913). Wallace's role is often played down or ignored altogether. Yet a hardcore group is convinced that herein lies a scientific conspiracy to cover up the fact that Darwin stole his groundbreaking theory from Wallace.
Evolution was not a new idea when Darwin outlined his theory. His grandfather, Erasmus Darwin, had written about changes in species, and others - including Edward Blyth, a museum curator, and Patrick Matthew, a wealthy Scottish landowner - had recorded variation in plants and animals, a form of natural selection. But there is no evidence that Darwin knew about Blyth's and Matthew's work before he developed his own ideas.
The case of Wallace is much more interesting. Born in the village of Llanbadoc, near Usk in Wales, he was not from the same elevated social class as Darwin. His father was a bankrupt failed solicitor and, although Wallace attended grammar school, he never went to university, instead training as a surveyor. But in 1848 he travelled to the Amazon with the intention of discovering the origin of species, inspired partly by reading Darwin's The Voyage of the Beagle.
A self-taught naturalist, Wallace earned his living by sending specimens back to private collectors and museums in England. His first journey ended in disaster when, on the return voyage, his ship caught fire and sank, taking his vast collection with it. Using the insurance money he arranged a second trip to the Malay Archipelago, and it was here that he conceived his idea of evolution.
Early in 1858, suffering from malaria and confined to his bed, he recalled an essay on populations by Thomas Malthus (coincidentally, the same essay that inspired Darwin), describing how natural disaster and starvation kept populations in check. It hit him in a flash - only the fittest would survive. He wrote down his ideas and sent them to a client who had complimented him on an earlier article he had written about species: Charles Darwin. When Darwin received Wallace's letter, he was devastated.
Darwin had not sailed on the Beagle intending to find the origin of species; his passage was secured as a companion to the captain, Robert FitzRoy, and he spent most of his time looking at the economic and geologic importance of the various countries the ship visited. His notebooks contain three times as many notes on geology as biology. The only time Darwin ever described himself as a scientist, he wrote "I, a geologist", and his first scientific theory (how island arcs form) was geological and still holds today.
But what of any conspiracy? Darwin claimed to have received Wallace's bombshell letter on 18 June 1858. At the time, he was writing a major work on evolution. His famous book, On the Origin of Species, is actually just a short abstract from this unpublished book.
Precisely when Darwin received the letter is important. Conspiracy theorists suggest that he received it up to a month earlier than claimed because, in the original manuscript of his book on evolution, there is a section of inserted material outlining his ideas on natural selection. Did Darwin receive Wallace's letter, realise that he had come across the best explanation for how evolution happens - by natural selection - and copy his ideas? Wallace's original letter and manuscript have been lost; they were last recorded in the possession of the geologist Charles Lyell.
Darwin was left distraught by Wallace's letter. He wrote to Lyell, saying "all my originality is smashed", and went on to claim that, "I would far rather burn my whole book than that (Wallace) or any man should think that I had behaved in a paltry spirit." The letter to Lyell is assumed to be dated 18 June, although there is no month written on the original.
Lyell had warned Darwin some years earlier that Wallace was working on evolution and had urged him to publish. Darwin, however, wanted to build a watertight case for the cherished idea he had been working on for more than 20 years.
Wallace's letter could not have arrived at a worse time. Darwin's daughter Etty, 14, was very ill with diphtheria and his 18-month-old son, Charles, was soon to die of scarlet fever. Lyell and the botanist Joseph Hooker - another of Darwin's friends - worked out a compromise, putting Darwin and Wallace's works before a meeting of the Linnean Society of London on 1 July 1858. The rest, as they say, is history.
So where does the truth lie? While there are intriguing mysteries surrounding the announcement of evolution, no historian of science seriously considers that Darwin stole the theory from Wallace or anyone else.
The person to ask, of course, would be Wallace. He never complained about his treatment or tried to claim priority. In fact, he was thankful to Lyell and Hooker for their elegant and even-handed solution: a joint publication.
Indeed, Darwin's best defence against conspiracy comes from Wallace himself, who published his own book on evolution in 1889, self-effacingly called Darwinism. In the introduction, he proclaimed that he was "more Darwinian than Darwin", a statement he would hardly have made if he felt that his best idea had been stolen.
James Williams is a lecturer in science education at the University of Sussex's School of Education and Social Work
TES partner English Heritage has shared an extensive resource to inspire pupils to think about Darwin.
See how pupils re-created Darwin's archipelago experiments in Bolton with TeachersTV.
Key stage 1: what do humans and plants need to grow?
Darwin was fond of collecting plants and other curiosities. Teach pupils about the interrelationship between humans and plants with a lesson plan and worksheet from the Hamilton Trust.
Key stage 2: Darwin's story
For a colourful depiction of Darwin's life, try Zsuzsi77's storybook.
Key stage 3: why was Darwin the most dangerous man in England?
Take a look at HilaryPegum's card-sorting game for developing debate on the conflict between Darwin and the religious thinkers of his time.
Key stage 4: Darwin jigsaw
A special task from collaborative for Darwin's birthday, which introduces pupils to his life and work.
Key stage 5: evolution speed dating
A fun, fast-paced revision game shared by Docras.
Find all links and resources at www.tes.co.ukresources019.
Original headline: A case of survival of the fittest?