The opening paragraph of the Wikipedia entry for Constantine Rafinesque notes that he was:
It then continues:
Rafinesque was eccentric, and is often portrayed as an “erratic genius”. He was an autodidact who excelled in various fields of knowledge, as a zoologist, botanist, writer and polyglot. He wrote prolifically on such diverse topics as anthropology, biology, geology, and linguistics, but was honored in none of these fields during his lifetime. Today, scholars agree that he was far ahead of his time in many areas.
[H]e saw much of what Darwin saw, could feel with his antennae the knowledge that would be Darwin’s glory…Darwin himself acknowledges Rafinesque in The Origin of Species. He quoted a sentence from New Flora and Botany of North-America, albeit begrudgingly. In a letter to a colleague, Darwin writes: “Poor naturalist as [Rafinesque] was, he has a good sentence about species and var[ietie]s, which I must quote in my Historical Sketch and I sadly want the date at once.” The good sentence was this: “All species might have been varieties once, and many varieties are gradually becoming species by assuming constant and peculiar characters.”
But in reality Darwin had little idea how far Rafinesque had gone. In a letter of 1832 to Torrey, Rafinesque wrote:
The truth is that Species and perhaps Genera also, are forming in organized beings by gradual deviations of shapes, forms and organs, taking place in the lapse of time. There is a tendency to deviations and mutations through plants and animals of gradual steps at remote irregular periods. This is a part of the great universal law of perpetual mutability in every thing. Thus it is needless to dispute and differ about new Sp[ecies] and varieties. Every variety is a deviation which becomes a Sp. as soon as it is permanent by reproduction.
One reason the scope of Rafinesque’s ideas in this area wasn’t known to Darwin or anyone else for so long is that Rafinesque had buried their boldest expression in his unreadable poetry. The lines dealing with evolution are in fact some of his least awful, as you feel him, for a second, stop versifying and start thinking: “Just like a tree, with many branches, most Of genera produce the various kinds of Or[sic] species; varieties at first, like buds Unfolding, and becoming species, when By age, they may acquire the proper forms.”
The proper forms-you see his needle start to twitch there. Also, “constant characters,” in the sentence Darwin references. He got close. Often when he approaches this question you can watch him–with a sudden flourish of meaningless, euphonious adjectives–trace a broken silhouette around the answer, as when he talks about “the natural evolution of spontaneous vegetable life exerted in wisdom thro’ ages” or about “fixed forms, and those that may vary to produce breeds or proles, until these assume the specific rank by important features, united to permanency, multiplicity of individuals or insulation in distinct climes.” Distinct climes! He was almost there–but the interior of the silhouette remains forever a vista of fog.
A remarkable anticipation of the central principles of evolutionary theory, even if not clearly and distinctly articulated.