There's two relatively recent well-received biographies of Darwin written by academic historians that deal with Darwin's death: 1991's Charles Darwin by Adrian Desmond & James Moore, and 2002's Charles Darwin: The Power Of Place, the second in a two-volume series written by Janet Browne.

Darwin, around when he turned 73 in February 1882, had fallen ill with heart pains, and doctors had travelled to his country estate to see him, partly because of his longstanding relationships with people in the medical profession. According to Browne, Darwin was clear-headed, with a sense of humour, in his final months. Additionally, he was still working on botany experiments with his son Francis two days before his death in April 1882; this is likely is not the final actions of someone who didn't believe in his theory.

Additionally, Darwin being honoured after death with a spot in Westminster Abbey suggests that the English religious establishment, by 1882, wasn't actually that universally outraged by his theories and their theological implications. Darwin himself was somewhere between a deist and an agnostic, like many freethinkers of his age, rather than an out-and-out atheist. He felt that the universe may well have been created by some creator, but he didn't believe that this creator had guided creation after that. Darwin had quietly rejected the Christian religion specifically, but he was not a firebrand like Thomas Huxley or Richard Dawkins, and he didn't want to hurt people's feelings - he spent years not publishing The Origin Of Species, even though he thought it was true, out of a very English sense of propriety. When he did finally publish it because Wallace had written to him with the same basic principle of natural selection and so he needed to explain his ideas, he was saddened by the way it upset people. He also found the letters that out-and-out atheists wrote him in his later life quite distasteful, feeling that they were going too far. But I digress.

The Desmond & Moore book doesn't mention the deathbed conversion story at all. Janet Browne categorically denies it: "there was no deathbed conversion, no famous last words."

James Moore, in 1994, wrote a book called The Darwin Legend, which tried to get to the bottom of the deathbed conversion story and where it had come from (apparently because when he was promoting his 1991 book with Desmond he kept getting asked about it). The most common source for the story seems to have been via Elizabeth Cotton, Lady Hope, who was a prominent figure in the temperance movement. In 1915, Lady Hope told a Christian conference in Massachusetts that she had met Darwin on his deathbed, and that she had found Darwin reading the book of Hebrews in the Bible; she soon then published an account of the meeting in a Baptist magazine. Darwin apparently told her that he'd been 'a young man with unformed ideas' and that she should speak to his servants about the Bible.

However, Darwin's children certainly seem to think that there was no deathbed conversion, and contradicted Lady Hope in very strong terms. According to Moore:

"The Darwins consistently denied the deathbed legend, and rightly so. Any claim about a deathbed scene, a recantation, or a religious conversion was indeed 'a work of imagination' (Francis Darwin), an 'absurd fiction' (Bernard Darwin), or a 'myth' (Nora Darwin)."

Additionally, according to a 1985 biography of Darwin by Ronald Clark, Darwin's daughter Henrietta specifically attempted to refute Lady Hope's version of events (unaware that there was evidence they'd met):

"I was present at his deathbed," she wrote in The Christian for February 23, 1922. "Lady Hope was not present during his last illness, or any illness. I believe he never even saw her, but in any case she had no influence over him in any department of thought or belief. He never recanted any of his scientific views, either then or earlier. We think the story of his conversion was fabricated in the U.S.A. . . . The whole story has no foundation whatever."

Research by Moore suggests, however, that Lady Hope had visited Darwin. But this was about seven months before his death, rather than in his final illness, and Darwin was not bedridden at the time. So Lady Hope's account should be taken with more than a grain of salt. Lady Hope, after all, was telling the story more than 30 years after Darwin's death, and the story had clearly ...evolved.

However, there was one way in which Darwin had - sort of - 'revoked' his theory of evolution before his death: in later editions of The Origin Of Species, Darwin softened his theory to take into account points he could not currently explain, allowing for the possibility that there were also Lamarckian mechanisms that contributed to evolution. Because Darwin didn't know about Mendellian genetic theory, let alone the structure and function of DNA, he had trouble explaining the basis of natural selection. In fact, until the 'modern synthesis' of evolutionary theory and genetic theory - based on an understanding of DNA that was only possible after Crick and Watson (and Franklin) - mainstream biologists did have question marks over Darwin's theory.

In any case, the modern acceptance of evolution by natural and sexual selection via DNA is not solely based on what Darwin said 150 years ago. From this point of view, if Darwin had recanted on its deathbed, it wouldn't matter. Scientists, for better or worse, tend to distrust theory on its own, wanting to see a theory's hypotheses confirmed by what they consider to be strong evidence. As a result, the modern acceptance of evolution via natural selection is based on a wide range of research in a lot of different fields, from palaeontology to genetics to ethology, by a lot of people over many years.

And while the fact of evolution is accepted - as it had generally been by biologists before Darwin, though they had different explanations for why it happened - and natural selection is accepted as the mechanism behind much evolution, there are still scientific controversies about the extent of natural selection as a driving force in evolution. The DNA sequencing technology that became available from the 1990s seems to suggest that natural selection was a weaker (but still present) force than Richard Dawkins claimed in books like 1979's The Selfish Gene, and that many changes to the genome are there simply because there was a mutation that had no real effect whatsoever (rather than because those mutations gave animals an advantage) which just happened to promulgate through a species through random chance rather than 'survival of the fittest'. Even Dawkins - not a man inclined to changing his mind - grudgingly admits this in his 2009 book The Greatest Show On Earth: The Evidence For Evolution.

Which is to say that if it did turn out tomorrow that Darwin had signed a deathbed confession and converted to Christianity, it wouldn't matter much to scientists; they'd say, "oh, he was an old man then, and his faculties were a bit clouded, and besides, what about all the DNA evidence?"