If you google "proust duel”, the top hit is Wikipedia’s List of Duels including the 25-y.o. Marcel's with Jean Lorrain on Feb. 5, 1897. "Proust and Lorrain exchanged shots at 25 paces. Proust fired first, his bullet hitting the ground by Lorrain's foot. Lorrain's shot missed, and the seconds agreed that honor had been satisfied." The footnoted authority is Douglas W. Alden's article in Modern Language Notes February, 1938. Alden claims "Such impetuosity is not surprising in a ‘nerveux,’ nor is this dramatic gesture astonishing in a young man, who, at this time, took feudal society seriously." The occasion for the duel was Lorrain’s scathingly criticle review of Proust’s Les plaisirs et les jours, which appeared in Le Journal, Feb. 3, 1897 — unfortunately, not the source of the “delicious” pregnancy quotation in Steve's post nine days ago (v.i.).
5/2/15 update: Gottschall's book references Barbara Holland's Gentlemen's Blood for the delicious quotation. She, however, references nothing! Under those circumstances one has to wonder what sort of scholarly pretension Gottschall was striving to maintain. (As in, "yeah, I heard some guy in a bar once say that.")