The Theory of Evolution was the greatest scientific concept of its age. It was so revolutionary that its author, Charles Darwin, revealed to a friend in 1854 that even mentioning it felt like 'confessing a murder'. Both the man and his theory are still the subject of intrigue and debate. How was it that the unremarkable younger son of a rich plutocrat, who idled through school, dropped out of medical studies and looked destined to be a clergyman of some quiet country parish, came to lay the foundation stone of modern biology? And how was it that another biologist, Alfred Russel Wallace, came up with the same theory at the same time?