When I began work on my book Straight: The Surprisingly Short History of Heterosexuality , I often got teased by friends who wondered whether, in working on the history of something so commonplace, I was going to come across anything that wasn't already common knowledge. Surely, they thought, it would all be very straightforward, very vanilla, very Leave It to Beaver, and if there were anything in there they didn't already know about, they'd be surprised.

As it turned out, this was far from true. The history of heterosexuality is actually a motherlode of remarkable and sometimes deeply strange stuff, from the broad-brush conceptual to the kinds of tidbits you add to your cocktail-party repertoire. Not only does the history of heterosexuality offer up surprises that make you rethink what "heterosexual" is and means, it also makes you realize how little we really know about this thing about which most of us assume we already know everything we need to. The following are 10 of my personal favorites.