David M. Buss believes that sex isn’t just for pleasure and reproduction.  He's an evolutionary psychologist and a professor at the University of Texas, and he spoke about everybody’s favorite topic at the American Museum of Natural History on February 3rd.

His research uncovered 237 distinct motivations for why humans have sex. Of the ones he found most surprising: revenge. He told the Museum, "Some people have sex to get revenge on a friend who has “mate poached” their partner or to punish their own partner." 

His lecture summarized of years of research, covering everything from the mating rituals of elephant seals to the Tiwi tribe of Australia, in which female children are married off at birth.