'Cynopithecus niger, in a placid condition' and 'when pleased by being caressed,' Studies for Darwin’s Expression of the Emotions of Man and Animals, 1872, c. 1871–72
Black chalk, heightened with white
Joseph Wolf’s scenes of life in the wild closely corresponded to Darwin’s vision of a perpetual 'struggle for existence,' and the two men became friends. Darwin invited Wolf to provide illustrations for Expression of the Emotions of Man and Animals, although in the end only these two drawings were used. Darwin wanted to demonstrate that at least some species of monkeys smiled like humans, proving a genealogical link. But Wolf himself was unconvinced, later telling his biographer that he 'never believed that that fellow was laughing, although Darwin said he was.' This incident exemplified the difficulties both in interpreting animals’ expressions and in recording them convincingly.
Darwin Papers, Cambridge University Library.
See The Struggle for Existence section for other works by Joseph Wolf.