Ideas are like living things. They operate in the busy cultural wilderness of our communal minds, symbiotic with millions of other Ideas. They are unconsciously engaged in a fight to survive and reproduce in order to sustain their species. And they are subject to the laws of Darwinian natural selection when doing so.
The Idea of "Natural Selection" itself had a pretty rough ride to fruition (and of course it's still evolving today). In the early nineteenth century it was setting off on its own private journey within the mind of a young Charles Darwin. It was not alone - his mind was already rich with other wild Ideas that had seeded themselves from the contemporary scientific and philosophical conversation. There was the early position of the French naturalist Buffon, who in the late eighteenth century, argued that all the world's four-legged animals had developed from just 38 originals. There was the proposal of Buffon's contemporary and sparring partner, Lord Monboddo, a Scottish lawyer, who, after studying the "origin and progress of languages" suggested that humans were once without language, and had evolved language skills in response to a changing, challenging environment. There were the words of Darwin's own grandfather, Erasmus Darwin, who asked in his Zoönomia (1796): "would it be too bold to imagine that, in the great length of time since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind, ...that all warm-blooded animals have arisen from one living filament, which the great First Cause endued with animality, with the power of acquiring new parts, attended with new propensities, directed by irritations, sensations, volitions and associations, and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down these improvements by generation to its posterity, world without end!" There was the discovery of another Frenchman, Georges Cuvier, who, in the same year, established that the extinction of a species was possible by examining the bones of pre-existing elephants. There were the claims of the infamous Lamarck, who in 1809 proposed his theory of use and disuse - the first imagined mechanism of evolution - and invented the phrase that so focused the young Darwin: "the transmutation of species." There was the influence of Robert Jameson from Edinburgh, who taught the teenage Charles Darwin a course in natural history that closed with lectures on the "Origin of the Species of Animals" and who first used the word "evolve" in the modern sense. And there was the scandalous work of the anonymous author of the Vestiges of the Natural History of Creation , a book that, in 1844, fifteen years before Darwin would move to publish, propelled the talk of evolution with such heresies as "...how can we suppose that the august Being who brought all these countless worlds into form by the simple establishment of a natural principle flowing from his mind, was to interfere personally and specially on every occasion when a new shell-fish or reptile was to be ushered into existence...? Surely this idea is too ridiculous to be for a moment entertained."
The primitive ancestor of Darwin's Idea came from this primeval soup of other Ideas and had to shuffle onwards through his busy brain, competing or falling into a symbiosis with each of these other Ideas, and navigating the greater environment beyond. We can partially track its course through "Darwin Country" by scanning the messy jottings and scribbles that Charles, the host, penned in a series of "notebooks on transmutation". For example, ten months after disembarking the HMS Beagle, in "Notebook B", p36, Darwin sketched the world's first "evolutionary tree". There had been other stick diagrams drawn by earlier evolutionists, but not with this implication - that species derive from a common ancestor, and that no creator is involved in their inception. Fourteen months after that Darwin recognised the presence of the Force in a short smudgy passage: "One may say there is a force like a hundred thousand wedges trying [to] force every kind of adapted structure into the gaps in the economy of Nature, or rather forming gaps by thrusting out weaker ones." The Idea was clearly still journeying!
Page after page, his notebook entries show slow progress. Often the thoughts and part-notions behind his words are indiscernible - he rambles - but each shuffle must have made its contribution because in November 1838, the Idea had reached a point whereby Darwin could confess to his wife, Emma, that he no longer believed that Life needed God. She wrote back in letters that she valued his honesty, but feared that his beliefs may now mean they would not be able to share the afterlife. On November 27th 1838, Notebook E, p58 he wrote a list:
"Three principles, will account for all
(1) Grandchildren. like. grandfathers
(2) Tendency to small change... especially physical change
(3) Great fertility in proportion to support of parents."
Number one is about inheritance. Number two is about variation. Number three is an allusion to a particular form of selection. The Idea was almost at the Promised Land, but in this form - as muddled musings - it wouldn't stand a chance in the broader environment outside Darwin's head; so it remained inside, journeying/adapting for another twenty years, until it was ready. In November 1859, it was finally formed in ink in the introduction of On the Origin of Species:
"As many more individuals of each species are born than can possibly survive, and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form."
There are numerous ways in which one could word Darwin's Idea, but it's important to realise that the words are just a front. Behind the words is an Idea that shuffled through a difficult territory for over twenty years; beginning poorly-adapted, and primitive, but, en route, becoming finely-adapted, advanced. It reached the Promised Land, in this case mass publication. Presumably, had it journeyed through the landscape of other minds at that time, the outcome would have been different. Over the same time period, Thomas Henry Huxley, the man who would later brand himself "Darwin's bulldog" and defend this Idea in every significant debate, had a mind that completely barred the passage of any Idea on evolution. Darwin's Idea would have never found a route through Huxley Country. Yet when he eventually experienced an advanced variant of Darwin's Idea, he was compelled to exclaim: "How extremely stupid not to have thought of that!" Was Huxley stupid not to have thought of that? Was Darwin a genius because he did? Or was it the nature of the selective environments in each of their minds that pre-destined intellectual history?