One life gives birth to another, it seems all species know this fact, but there is one specie that goes beyond this scientific theory; Humans. Humans are the only ones who believe that sex is also a way to attain pleasure.
Many of us do consider this as appropriate but some of us have gone beyond the natural way of copulating. Some men often indulge in unnatural ways of getting sexual pleasure; they term it as their sexual fetish. Some can be accepted up to an extent but some are unbearable like having sex with inanimate objects.