The originality of the idea behind one of the great scientific discoveries - Darwin's theory of evolution - has been questioned by a Cardiff academic.
Professor Pearson found the theory in a 2,000-page account
A theory which predates Charles Darwin's 1859 book, On the Origin of Species by Means of Natural Selection, has been discovered.
An account of natural selection has been found in a document dated 1794.
Professor Paul Pearson from Cardiff University tracked down the earlier publication by geologist James Hutton in the National Library of Scotland.
In the middle of the second volume of the 2,000-page account is a chapter on the selection theory.
Darwin studied in Hutton's home town of Edinburgh, which at the time was famous for its scientific clubs and societies.
Professor Pearson said: "There is no question of Darwin knowingly stealing Hutton's idea.
"But it is possible that an old half-forgotten concept from his student days later resurfaced, as he struggled to explain his many observations on species and varieties made voyaging around the world in HMS Beagle.
Darwin left an indelible mark on society
"Darwin rightly gets the credit for applying the principle to the transformation of species and assembling the evidence that convinced the scientific world."
Darwin was born in 1809 in Shrewsbury and went to Cambridge University to become a Church of England clergyman after quitting Edinburgh University.
His observation of different types of finches on the Galapagos Islands - also famed for its giant tortoises - also helped mould his ideas.
He became an unpaid naturalist in 1831 on the HMS Beagle for a five-year scientific expedition to South America.
When he returned to England in 1836, Darwin used his knowledge of the animal and plant life he had seen to try to solve the riddle of how species evolve.
He worked on his theory for twenty years, and was prompted to act by a letter from Alfred Russel Wallace, who had come to almost identical conclusions.
They published a joint paper, and in 1859 Darwin published the book which wrote his name into history.
He later lived with his wife and children in the village of Downe, near London. Darwin died on 19 April, 1882, and was buried in Westminster Abbey.
There was strong resistance to Darwinian thinking but nowadays the theory of evolution is at the centre of mainstream science.