And now for a lesson in art and anthropology...
The Moche were an ancient Native American civilization that flourished in northern Peru from about 200 AD to 700 AD. Also known as the Mochica people, they were farmers with no written language, yet their culture was sophisticated enough to produce pottery depicting their sexual lives. They seem to have had a predilection for oral and anal sex. For more examples of Moche art, click here.
According to Wikipedia, "While anal intercourse, fellatio, masturbation and cunnilingus were commonly depicted on Moche pottery, vaginal intercourse was only depicted when the male involved wore ceremonial garb, the female had two braids which ended in snake's heads, and the copulation occurred under an elaborate roof of a ceremonial building. In these scenes of procreative sex, additional figures are always depicted watching the couple in the building and holding their hands as though in supplication."
Moche Art and Archaeology in Ancient Peru (Studies in the History of Art Series), Sex, Death, and Sacrifice in Moche Religion and Visual Culture, Moche Portraits from Ancient Peru (Latin American and Latino Art and Culture)
There's a novel entitled The Moche Warrior. It's the third book in Lyn Hamilton's Lara McClintoch's Archaeological Mystery Series.