User blog:MrHatNClogs/Shinigami origins???

Shinigami. Kubo has given us very little info on their origins. So my question is wether Shinigami are spiritual beings born in the soul society ( kinda like angels are created in heaven, not that im religious) or are they just souls of the dead who where sent to the Soul Society from earth ages ago, and aquired serious spiritual power through living in the soul society for a prolonged period of time?? Looking 4ward to your thoughts and please provide references in your answers. Thanx ;D