A soul is an incorporeal, insubstantial "essence" that constitutes part of the definition of an individual human. In distant prehistory, back in the mists of antiquity, those hominids who would one day be humans began to evolve what can best be described as a 'psychic organ'. While this organ had no physical component, it nonetheless was a real adaptation in neo-mankind's non-physical consciousness. This "mutation" bred true, and proved its survival value, and thus, was passed on to succeeding generations.