Board Thread:Naruto Discussions/@comment-36221354-20180717114536/@comment-1512913-20180717161650

It's not true. There is Momoshiki whose Rinnegan predates Hagoromo in all likelihood and there is no evidence of Sharingan. Just because Hagoromo had the Rinnegan and Indra the Sharingan, people assume Asura's chakra upgrades the Sharingan into Rinnegan, except it doesn't, otherwise Obito and Danzo would have awakened the Rinnegan.

In other words, the Sharingan isn't a prerequisite of the Rinnegan.