https://phys.org/news/2018-05-classics-darwin-species.html

Indeed in this age of the counter-factual and pseudo-factual, acquaintance with the foundations of our scientific tradition—and insights into the struggles of their creation—seems a matter of some urgency.

In the introduction alone, we learn that Darwin first conceived of his theory when travelling the world as a naturalist on board HMS Beagle (1831-6), that he had kept collecting data in support of it ever since, that he even wrote a rough draft (he calls it "a sketch of the conclusions") many years earlier, and that he was prompted to publish it (20 years later) only because his contemporary Alfred Russel Wallace had recently sent him a "memoir" reaching a similar conclusion.