At Cambridge University Library, along with all the books, maps and manuscripts, there’s a child’s drawing that curators have titled “The Battle of the Fruit and Vegetable Soldiers.” The drawing depicts a turbaned cavalry soldier facing off against an English dragoon. It’s a bit trippy: The British soldier sits astride a carrot, and the turbaned soldier rides a grape. Both carrot and grape are fitted with horses’ heads and stick appendages. ‘The Battle of the Fruit and Vegetable Soldiers,’ a drawing on the back of a manuscript page from Charles Darwin’s ‘On the Origin of Species,’ attributed to Darwin’s young…