Missionary position

"In general, early modern Catholic doctrine held that sexual relations were acceptable as long as they were within marriage, not done on Sundays or other church holidays, done in a way which would allow procreation, and did not upset the proper sexual order, which meant the man had to be on top (what has since been termed the “missionary position”)."

"One presumes that all of those jokes about the missionary position might have a kernel of truth."

"Bonobos and humans enjoy many different copulatory positions, with ventral-ventral (missionary position) appearing to be preferred by bonobo females and rear-entry by males, while chimps prefer rear-entry almost exclusively."