Is it a coincidence?

As I was looking up information for the film "Adaptation," as is per usual on any wikipedia search, I started to follow links that would feed me potentially interesting, though not particularly useful information. When I clicked on the link for orchids, I was somewhat surprised to find that Darwin, in his later years, had done research on the cross-pollination of orchids, featured in his book, "Fertilisation of Orchids," from 1862. While I do think it is interesting that a prevalent theme of the film revolves around orchids, I do not think it is a coincidence that they were featured in the movie, and that Darwin, who even makes a sort of 'cameo' appearance, studied them. I think that they way in which Charlie Kaufman incorporates all of these hidden elements into the movie is a part of why it was such a strong movie. The book off of which the film is based, "The Orchid Thief," does not seem, as the movie also points out, to have anything to drive the plot, which is perhaps why the writer chose to subtly incorporate Darwin into the film; something like a silent respect for his research. And  because the film is about the evolution of characters, it would seem only fitting to have Darwin present for a representation of the idea he is famous for. So is it a coincidence that both the real and the fictional Charlie Kaufman were trying to adapt "The Orchid Thief," and ended up with a reflection on Darwin, or was it carefully mapped out?