Sex is a seemingly inescapable reality of the biological world. Surveying the animal and plant kingdoms, at least, seems to reveal a world distributed into male and female. But the ultimate cause of sexual difference was a mystery even to Darwin. Soon after the publication of the Origin of Species a botanist named Charles Daubney wrote to Darwin and provided a series of concrete statements about the origin of sexual variation. Darwin was not so confident and in his reponse to Daubney, called sexual difference “one of the profoundest mysteries in nature.” (see the letter)
Challenging Daubney’s argument that asexual reproduction only produced a copy of the parent, Darwin provided numerous examples of plants which produced sexual variation through asexual propagation. Darwin was more inclined to see sexual reproduction as a check on variation, stating in his notebook, “`My theory gives great final cause … of sexes …: for otherwise, there would be as many species, as individuals….” (Notebook E p. 48-49). However in the Origin Darwin only went so far as to make a general comment on the biological explanation for sexuality, “it is a general law of nature … that no organic being self-fertilises itself for an eternity of generations” (Origin, p. 97). While key to Darwin’s theories, sexual difference was an issue which remained open to debate throughout the nineteenth century — a fascinating point to bear in mind as we contemplate his attitudes toward gender.