The human-like qualities of great apes have always been a source of scientific and popular fascination, and no less in the Victorian period than in any other. Darwin himself, of course, marshalled similarities in physiology, behaviour and emotional expression between Homo sapiens and other simians over the course of his long career to support his views on evolution. This kind of evidence appeared in many of his publications, notably The Descent of Man and The Expression of the Emotions in Man and Animals. But were some parallels between human beings and other great apes too disquieting to use as scientific evidence?
Correspondence between Charles Darwin and Gaston de Saporta, a French paleobotanist, suggests that this may indeed be the case. In 1872, de Saporta wrote to Darwin after reading Descent of Man. In a long letter in which he both praised the work and expressed his opinion that Darwin may have argued for too close a common ancestry for man and monkey, de Saporta identified two key pieces of evidence which he believed showed most strongly the commonalities between humans and apes: dentition, which “seems to denote an exclusive link with the Monkeys of the old continent,” and “female menstruation and, as a corollary, the odour which makes women attractive to many monkeys.”
In his reply, Darwin graciously thanked de Saporta for “the trouble which you have taken in giving me your reflections on the origin of Man.” Promising to reflect on de Saporta’s comments, he nonetheless stood his ground:
I cannot at present give up my belief in the close relationship of Man, to the higher Simiate. I do not put much trust in any single character, even that of dentition; but I put the greatest faith in resemblances in many parts of the whole organization, for I cannot believe that such resemblances can be due to any cause except close blood-relationship.
It’s no accident that Darwin did not acknowledge de Saporta’s point about menstruation or its corollary—the attractiveness of human women to other apes. Darwin’s difficulty negotiating this issue had much to do with norms of Victorian respectability, and what was or wasn’t appropriate for wider circulation beyond private correspondence or, for publication.