Board Thread:Naruto Discussions/@comment-29393962-20161111215453/@comment-24824859-20170114114341

@Ravenlot27 SPSM is not something one can awaken on his own. It can only be given by Hagoromo unlike the Rinnegan where you can awaken it by yourself (with the components of course). Asura's descendants are just as capable using dojutsu, when given the chance, as Indra's descendants as seen with Nagato. BZ still stated that he approach reincarnates of both Indra and Asura. He was more inclined to convincing Indra's reincarnation because they were more willing to awaken the Rinnegan, not more capable.

The Rinne-Sharingan and Sasuke's "Sharinnegan" are proof that the Rinnegan doesn't come from the Sharingan and thus, the Sharingan is not a requirement to awakening the Rinnegan