His theory on evolution has influenced many science disciplines

A Cambridge historian with access to Darwin's papers says there is simply no evidence to show the naturalist held back his evolution theory.

Dr John van Wyhe says the scientist was just busy with other writings and also sporadically hindered by ill-health.

His analysis of events is published in a journal of the Royal Society.

"If you read his letters from the 'gap years', as I call them, there are many references to his friends and relatives about what he intends to do with his theory - and that is to publish once he has finished his other work," Dr van Wyhe told BBC News.

"The problem was that 'other work' took him far longer than he expected."

The other work in question included writing up the detailed descriptions of animals, plants and rocks he saw on his career-defining voyage to the Galapagos Islands on HMS Beagle.

In particular, it seems, he spent an inordinate amount of time describing new barnacles - a personal passion.

'Consistent' line

Charles Darwin's seminal work On the Origin of Species by Means of Natural Selection was first published in 1859. In its opening pages, he refers to his realisation of its central ideas coming to him in 1837.

Various explanations have been offered for the 22-year wait to get into print.

Some say he procrastinated because he feared scorn from scientific colleagues, others that he was concerned about persecution by the church; some even that his ideas might have annoyed his religious wife, or reflected some deep inner psychological turmoil.

Dr van Wyhe says close examination of Darwin's papers and publications show him to be consistent in his determination to publish.

Slow burn

"Darwin was aware that his theories would be despised but that does not mean he was afraid of saying what he believed," the scholar added.

"His project was highly ambitious and of immense scope and he needed time to garner the necessary evidence. But he was also working on other projects - his Beagle-related works, then his work on barnacles - and these pushed back the date until he could start work on his species theory."

Dr van Wyhe says the "delay view" appears to have gathered pace in the 1940s, probably inherited from earlier writers who did not have access to all of Darwin's work.

He says the long gestation was typical of the way Darwin worked. The naturalist's book on orchids was not published until 30 years after that research began; he published his earthworms book 42 years after first conceiving the idea.

When On the Origin of Species did finally go to the printers it was supposed to have caused a sensation , although some now suspect the level of controversy, just like the significance of the gap years, has been exaggerated.

Darwin's observation that species evolve over the course of generations through the natural selection of favourable traits has become a central pillar of biological thinking and has influenced many other fields of scientific endeavour.

Dr van Wyhe details his arguments in the Notes and Records of the Royal Society.