Many authors are protective of their original drafts, but Charles Darwin allowed his kids to illustrate his original copy of On the Origin of Species. It’s likely the original draft was preserved by the family based on the sentimental value of these drawings, and the manuscript is now a part of an arts exhibit at the Cambridge University Library.

Darwin and his wife Emma had ten children, and though it’s not always clear which children made their mark on which pages, the twenty-three pages of illustrations feature lively images of birds and plants. One memorable drawing by his son Francis depicts fruits and vegetables in battle.

Robert L. Dorrit, a professor at Smith College, wrote of the drawings, “Contrary to the stereotype of the dispassionate scientist… Darwin was a man to whom family and friends mattered profoundly, and many poignant objects in the exhibition remind us of his humanity.”

The images are incorporated into “A Voyage Round the World,” a new exhibit at the Cambridge University Library that is focused on Darwin’s trip on the H.M.S. Beagle. Darwin published a travel memoir in 1939 about the second trip on the Beagle (the book was originally titled Journal and Remarks but commonly known as The Voyage of the Beagle). Scheduled for a two-year journey, the ship set off from Plymouth Sound on December 27, 1831 and did not return until October 2, 1836.

John Wells of the Cambridge University Library told the Telegraph that the original draft of the manuscript may not have survived without someone preserving it for sentimental value:

There are just thirty or so of these original sheets in existence and the vast majority have a child’s drawing on the back. It’s quite amazing to think these priceless historical exhibits have only survived because of a child’s drawings on the back. It demonstrates the importance of his family and brings it home that he surrounded himself with family, and friends, as he worked.

“The Battle of the Fruit and Vegetable Soldiers” by Francis.

The exhibition also includes the letter that first offered the 22-year-old Darwin a place on board, field notes, specimen lists alongside some of the plants and animals they describe, geological maps, sketches made by the Beagle’s artist (Conrad Martens), and some of Darwin’s books.

The library is displaying another twenty three sheets from the manuscript, and they believe there are about ten more illustrated pages in existence.