Board Thread:Boruto Discussions/@comment-31700161-20170610121821/@comment-27089028-20170611002457

◾ Although the Sharingan originated from Kaguya Ōtsutsuki's Rinne Sharingan, it was rumoured to be derived from the Byakugan.


 * even when the Rinnegan was later proven to exist, it was regarded by some as merely a mutation.

It's literally on the Wiki pages of the Rinnegan and Sharingan.