In his youth: Charles Darwin painted by artist George Richmond in the late 1830s.
"I have no great quickness of apprehension or wit," Darwin once wrote. "My power to follow a long abstract train of thought is very limited... my memory is extensive but hazy."
Darwin was born on 12 February 1809 in Shrewsbury, western England, to a wealthy family; his father was a doctor, one grandfather, Erasmus Darwin, was a noted natural philosopher and the other, Josiah Wedgwood, set up a famous pottery.
He was a reluctant student. After school, he went to Edinburgh University to study medicine like his grandfather, father and brother, but was bored by lectures and horrified by watching surgery without anaesthetic.
He started studying natural history in his free time, taking long walks on beaches near Edinburgh, where he hunted for shells and watched wildlife.
Darwin quit medicine and his furious father sent him to Cambridge University where he studied to be a clergyman, but it was the same story: he was more interested in collecting beetles than hitting the books.
Then his life – and, in no small measure, the history of the world – was turned on its head. One of his professors recommended him to Robert FitzRoy, captain of HMS Beagle, who wanted a companion for a two-year, round-the-world surveying mission.
The Beagle set sail in 1831, when Darwin was aged 22. The voyage extended to five years, taking in places like Brazil, the Galapagos Islands, Tahiti, New Zealand and Australia.
Despite chronic seasickness, the young man was thrilled, writing: "My mind has been, since leaving England, in a perfect hurricane of delight and astonishment."
Darwin collected a mountain of flora and fauna specimens, all of which were carefully tagged, and resolved to write a book on his discoveries when he returned home.
The Beagle docked in Britain in 1836 and Darwin, who never ventured abroad again, immediately buried himself in work.
He published Journal Of Researches Into The Geology And Natural History Of The Various Countries Visited By HMS Beagle, the book which made him famous, in 1839. But stress began to take its toll and the ill health which dogged him for the rest of his life took hold.
He agonised over whether to get married to ease his anxiety and drew up a list of pros ("constant companion... better than a dog, anyhow") and cons ("terrible loss of time") before concluding he must wed.
He married his cousin Emma Wedgwood in 1839 after a quick courtship. Theirs was a contented union which produced 10 children.
