Board Thread:Wiki Discussions/@comment-24477541-20140328180624/@comment-24753830-20140330114845

Indeed. It's possible that because the story goes so far into the past, the whole origin of the Sharingan itself was forgotten, or at least kept a secret after Indra's branch of the family was created in order to protect them from the downsides of the Mangenkyo... If that's the case, it's only natural that geniuses and knowledgeable people such as Madara and Izuna would look into such information to gather more power for themselves. That would also give them the title of "first shinobi alive to awaken the Mangenkyo Sharingan" after many generations that didn't know about it.