 If sex is universal, why do species go about it in so many different ways? And what can humans learn from the mating habits of the creatures of the animal world? Sex is the engine of evolution - the drive to mix genes to produce the strongest, fastest or most efficient specimen of the species has propelled all of creation to evolve, adapt and survive. Promiscuity, jealousy, violence, incest, suicide, cannibalism and indeed hermaphrodites all serve an evolutionary purpose - and in the animal world, monogamy is a "sexually deviant" behavior that serves no evolutionary intent.