Why would the Industrial Revolution affect what human beings find funny? I'm not sure I'm seeing the connection. Jokes about bodily functions, and sex in particular, have been written down for as long as we've had writing, and probably have existed for as long as we've been human. There's a Sumerian joke that gets mentioned on here a lot that goes to the effect that since the beginning of time women have farted into the laps of their husbands--it's a twofold joke, both joking about farting and about sex, since (as the notes to an edition of Gilgamesh I have somewhere around here puts it) "intercourse from the rear is well-attested in ancient Mesopotamia." Some of Aristophanes' favorite jokes are sexual--an entire comedy of his, the Lysistrata is pretty much entirely sex jokes. A reading of any of Shakespeare's comedies will show instantly that like half of his jokes are sexual in nature. For maybe an earlier medieval example, the Facetiae is basically a collection of fart, poop, and sex jokes. Erotic art and literature, humorous or not, is a constant feature of the ancient and medieval--I mean, what's not funny about nuns harvesting the fruit of the wiener tree? It's a serious and bizarrely common fallacy to assume that modern people invented sex--a lot of the stuff in our manuscripts is often quite shocking to students when they see it for the first time, even in the days of internet porn