With the creation of the luxury class came privileges. Some of these were the ability to pick and choose among the population the most desirable Sex partner. This usually came with the ruling class and to some lesser extent the warrior class. The first ruling classes were the Priest kings of Mesopotamia who it was believed had a regular line to the gods and could bring down blessings or curses from them.
With this sort of power it was no wonder that they could have Sex with whomever they chose. If the priest king wanted to fuck your wife or daughter you pretty much let him, to some extent. Even the fear of the gods did not always deter vengeance from a jealous husband, father or boyfriend. Of course this could also extend to the woman in the case that the priest king was gay and wanted the male. While most simply submitted to this practice there were others who were against it and secretly conspired against it. Most of the time they simply deposed the one and replaced him with themselves to continue the practice. It was not truly until the beginnings of democracy in the west that this practice of dictatorship combined with religious trappings found a rival. Then the idea of freedom began to spread and this began the process of unraveling the dictatorships.
This however has been a sticky process because it has always been and will always be in a mans nature to rule one over the other when possible and even in the modern democracy this is true. The truth of this bears out in the penchant for democracies to enter into a police state stage when so much power is concentrated into the hands of the few. The darker truth then would probably be that true democracy has rarely if ever actually been practiced among men and then only short lived.
Many people have heard of fisting, also known sometimes as handballing, where the entire hand of one lover is inserted into the orifice of another. Vaginal fisting is of course where 
