The original theory of evolution... were it not for the farmer who came up with it, 60 years before Darwin

He was a gentleman farmer who developed a passion for rocks at the height of the Scottish enlightenment in the late 18th century - a passion that eventually led him to become known as the father of modern geology.

Evidence has now emerged to suggest that James Hutton also formulated the theory of natural selection more than 60 years before Charles Darwin publishedOn The Origin of Species. A scientist and amateur historian has unearthed a little-known publication written by Hutton in 1794 in which is buried a description of the principle that lies at the heart of Darwin's theory of evolution.

Paul Pearson, professor of palaeoclimatology at Cardiff University, says there is no doubt that Hutton had independently formulated the theory of selection long before Darwin. "Although he never used the term, Hutton clearly articulated the principle of evolution by natural selection," Professor Pearson said.

It is likely Hutton's theory was still being discussed within the intellectual circles of Edinburgh when Darwin was there as a medical student, he said. It is even possible the memory of this half-forgotten concept may have resurfaced in Darwin's mind many years later when he was struggling with the theory that he finally published in his famous book of 1859, said the professor.

"It's not implausible and in no way is it dishonourable on Darwin's account. But it's possibly beyond a coincidence that the characters involved were all at Edinburgh," he said.

Natural selection is the driving force of evolutionary change and the mechanism that leads some individuals in a species to gain an advantage over others. Darwin was the first to formulate a coherent theory of how natural selection could change a species and how these gradual changes could lead to the evolution of new species.

For 30 years, Darwin struggled with the concept and amassed huge amounts of evidence in support of it until he was finally persuaded to go public when he realised that Alfred Russell Wallace had independently come up with the same theory.

Darwin was magnanimous enough to allow Wallace to publish his theory alongside his own. He also acknowledged two other authors who had also independently thought about the concept of natural selection some years previously.

One was Patrick Mathew, who had outlined the mechanism in an appendix to a book in 1831. The second was a physician, William Wells, who had speculated on natural selection and human evolution in 1818. But neither of these had given the thorough, detailed description and analysis of natural selection that Darwin formulated. Historians who have studied Darwin's extensive notebooks have also shown beyond doubt that Darwin had independently come up with the theory of natural selection and evolution. But what has intrigued Professor Pearson is that Hutton, Mathew, Wells and Darwin lived in Edinburgh at a formative time in their lives.

"It may be more than coincidence that Wells, Mathew and Darwin were all educated in Hutton's home town of Edinburgh, a place famous for its scientific clubs and societies," he says in a letter to the journal Nature. "There is no question of Darwin knowingly stealing Hutton's idea. But it is possible that a half-forgotten concept from his student days resurfaced as he struggled to explain his many observations on species and varieties made voyaging around the world in HMS Beagle."

Although it is known that Hutton dabbled with a theory similar to natural selection, the extent to which he had described his ideas in a published account had not been widely recognised until now.

Professor Pearson tracked down Hutton's three-volume Principles of Knowledge in the National Library of Scotland and discovered a long section on natural selection. "I was amazed to see a whole chapter on this theory. At the time of publication, the book was criticised for being too long and obscure. This section has languished in obscurity ever since," Professor Pearson said.

The chapter captures the essence of natural selection: that traits can be inherited and that certain traits can confer an advantage on offspring, which are therefore more likely to pass on these characteristics to subsequent generations.

Hutton writes that in a race of dogs that depends on "nothing but swiftness of foot and quickness of sight" for survival "the most defective in respect to those necessary qualities would be the most subject to perish". Meanwhile, "those who employed them in greatest perfection would be best preserved, consequently, would be those who would remain ... to continue the race". He even explained how the same "principle of variation" - a term used by Darwin - must influence plants "whether in a forest or meadow".

Professor Pearson said Hutton was a keen experimentalist who observed inheritance and variation among animals and plants because of his interests in farming. "These experiments led him to distinguish between seminal variation, which occurred in sexual reproduction and was heritable, from non-heritable variation caused by circumstances of soil and climate," he said.

Hutton had developed a concept of nature and nurture long before the discovery of genes. In one experiment, he showed that a plant growing under poor conditions did not lose its ability to flourish in subsequent generations if its seeds were grown in rich soil. But his claim to intellectual priority fails because he discounted the idea that one species could evolve into another. "He rejected the idea ... as a 'romantic fantasy'," Professor Pearson said. In common with many of his time, Hutton believed that everything was created by God for the benefit of man.

"Darwin rightly gets the credit for applying the principle [of natural selection] to the transformation of species and assembling the evidence that convinced the scientific world," Professor Pearson said.

How the theories compare

Hutton on the process of natural selection:

This wisdom of nature, in the seminal variation of organised bodies, is now the object of our contemplation, with a view to see that the acknowledged variation, however small a thing in general it may appear, is truly calculated for the preservation of things, in all that perfection with which they had been, in the bounty of nature, first designed. Now, this will be evident, when we consider, that if an organised body is not in the situation and circumstances best adapted to its sustenance and propagation, then, in conceiving an indefinite variety among the individuals of that species, we must be assured, that ... those which depart most from the best adapted constitution, will be most liable to perish, while ... those organised bodies, which most approach to the best constitution for the present circumstances, will be best adapted to continue, in preserving themselves and multiplying the individuals of their race.

Extract from Darwin's 'On the Origin of Species':

It may be said that natural selection is daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of time has marked the long lapses of ages, and then so imperfect is our view into long past geological ages, that we only see that the forms of life are now different from what they formerly were.