note: This is adapted from an email conversation I had recently.
Humans are nothing if not ingenious recyclers of their environment. I believe the ancient Romans used to clean their clothes with a brew that included urine procured for a small fee from urban pedestrians.
Contraception too has its roots in waste products. Women in pharaonic Egyptian used to employ a crocodile dung compound as a sort of spermicide. Apparently, this prophylactic fell out of use in the modern era. About the time Adam Smith was writing about the "invisible hand of Capitalism," Europeans were pinning their contraceptive hopes on the stopping power of lemons. I assume that there were other benefits to using a more palatable substance than crocodile excrement. Even considering the high level of filth that people lived with back then, I think an extra dollop of fecal mass (particularly that of a rare and exotic beast) would have had a deleterious effect on the libidos of all but the most sorely pressed of couples. Certainly if the Hindus had had only the Egyptian method available, the _Karma Sutra_ would have been a greatly abbreviated tome.