Caravaggio…Van Gogh…Darwin? Charles Darwin, of course, wasn’t an artist – in fact, he could barely draw – but he was a visual thinker. In the new book Darwin’s Pictures, art historian Julia Voss makes the case that Darwin relied on visual images to both conceptualize and communicate his radical theory of evolution.

In the late 19th century, scientific books were taking full advantage of printing techniques that allowed the use of engravings and imagery. Disciplines such as geology and embryology developed a clear visual language. Think of geologic cross-sections that compress space and time into a single image, for instance. But Darwin was creating this theory from scratch. Because his idea was so unprecedented, he had to invent his own visual language in order to communicate it.

Darwin was deeply preoccupied with images. His papers, now at Cambridge University Library, are full of drawings and sketches, both his own and artist renderings. In his travel notebooks, Darwin drew maps and diagrams while working on his theories. Later, he also worked with artists, taxidermists, and draftsmen to create explanatory illustrations for his books.

One of the images he “invented” is the now-famous time sequence, which lines up different species in hypothesized order of evolution. Darwin needed images like these to communicate his theory; Voss says that while it might take hundreds of pages of text to explain evolution, a single image could summarize the idea for a reader in a few seconds.

In the slideshow here, Voss talks about Darwin’s images and their impact. Much like Darwin’s theories, his images often had a life of their own.

Thanks to Yale University Press and Julia Voss. To read analysis of many more of Darwin’s images, check out Voss’ book, available here.