One more note on Darwin's The Origin of Species, whose 150th anniversary of publication was yesterday. The Origin was not just a scientific milestone, it was a publishing success story. It went through six editions in the space of 13 years after 1859. Darwin revised and expanded it from 150,000 to 190,000 words in response to the comments and critiques he received. (I was interested to learn that the word "evolution" did not appear until the sixth edition. I knew that it was the philosopher Herbert Spencer who coined the phrase "survival of the fittest," which he derived from Darwin's ideas; I didn't know that Darwin then borrowed it from him, including it in the fifth edition.)
Ben Fry has created an arresting animation that graphically unfolds the revision history of On the Origin of Species. Below is just a screenshot; the full animation is here.