Board Thread:Naruto Discussions/@comment-3232093-20140617193601/@comment-25228549-20140819102536

Maybe it was watered down through generations. Starting with Kaguya with the first Rinnegan, then Hagoromo, then Indra had the Mangekyo (if we're discussing the evolution of the Sharingan then the only logical thing is that evoulution goes backwards in this case), then the whole Uchiha bloodline with the Sharingan and MS.