Sex, since the history of man or human evolution has gone through several changes, even in terms of definition and form and the individuals engaging in it. Once upon a time, sex was thought to be primarily for reproductive reasons, then for the relief of sexual tension and later, for the sexual pleasure. Right from the explosive documentation of the Kama Sutra, various studies... http://www.jamolon.com/2016/06/some-whys-of-sx.html