The Byakugan Gave Birth to the Sharingan and Rennigan
I have reasons to believe that the Byakugan is the origin of all Dojutsu:
It was said that the Six paths Hermit discovered chakra, then used it to perform ninjutsu, thus making him the first ninja. But how eactly could he have seen the chakra without actually performing ninjutsu.
When the Sage began his journey into the ninja world, he gained a technique that allowed him to gain knowledge of chakra. A technique called Byakugan. As it was stated by Kishi, the Byakugan has the greatest insight than all other Dojutsu. It not only sees chakra as the Rinnegan and the Sharingan does, but it also sees their tenketsu, have a 360 degree range of vision, and teloscopic vision. This allowed the SO6P to gain knowledge about chakra & the chakra netwirk, and began to use it for himself.
This explanation seems logical, I mean, think about it, so far, the byakugan is the only known method to be able to see the chakra network in full detail.
As we all know and what has been stated by Kishi is that whoever possesses the Rinnegan will have the power to control all of the elements, and control the Yin and the Yang. The Hyuga clan, has the power of the 8 Trigrams. In Japanese, the 8 Trigrams represent all the elements.
During Hinata and Neji’s battle in the Chunnin exams, after activating their Byakugans, Kakashi states that there are rumors that the Uchiha’s Sharingan is possibly an off-shoot of the Hyuga’s Byakugan. Kakashi even goes on to state that the Uchiha clan itself possibly stems from the Hyuuga clan. Of course, this is but a rumor, however all rumors have an origin. Kakashi also states, as a fact, that the Hyuuga are the oldest clan of Konoha.
This goes to show that the Hyuuga do indeed pass the Uchiha in their birth/formation, which leads me to believe that the Byakugan to be a Dojutsu that came from the sage himself. This may also explain the two eyes’ similar colours and appearance.
Another thing to note is that Kakashi says something about the Rinnegan being a mutation, which could hold some truth.
So, according to Kakashi, the Sharingan came from the Byakugan, the Rennigan is a mutation, & the Hyuga are possibly the oldest clan in Konoha.
Now, a lot of you would just say Kakashi was wrong, but what if he wasn't?
Now, if we assume that the Six Paths Hermit did indeed have the Byakugan, which allowed him to discover chakra, then it would mean he had a dojutsu before he became the Juubi’s host.
After becoming the host, his Byakugan was affected by the Juubi’s Super-Sharingan, thus leading to a mixture between the Byakugan & the Super-Sharingan, creating the Hermit’s trademark eyes, the Rennigan. This in turn would mean the Rennigan is a mutation of the Byakugan.
Another point that can strengthen this theory is Naruto when he using Kuarama's Chakra. When Naruto is in Bijuu Mode, Kyuubi Mode, or in his chakra cloak forms, his eyes turn red due to the tailed beast chakra within him.
One note that I'd like to mention, though it may be minor and probably not really important, is the fact that the Byakugan & Rennigan have the same iris colour as their pupils, but the Sharingan doesn't.
the Rennigan itself looks like the juubi's eye without the Tomoes of it's sharingan & with a purple colour, & the Byakugan also has a slight purple to it.
As for how the Sharingan came around & how the Byakugan is still around...
My answer to that goes something like this. When the Elder son inherited his father's eyes, he, just like his father, got some of the Juubi's chakra inside him, but it remained dormant and didn't affect him much. But when his father died AND chose his younger brother instead of him to be his successor, he felt hate, jealousy, sadness, envy and anger , which caused the Juubi's sleeping chakra inside him to awaken and cause his white eyes to turn red. This in turn, would make the Sharingan an off shoot of the Byakugan.
Later on, some of the Elder son's desendants would inherit his juubi-infected eyes, the Sharingan, while others would be born with the Sage's eyes, the Byakugan.
One point that can strengthen this argument is the fact that, as seen in the following page, the Juubi has 9-tomes on his super-sharingan.
Yet, here, when it has been revived, it merely has three.
It's missing three tomes, which is coincidentally the same number as the Sharingan's tomes.
So, basically, the Byakugan came first, followed by the Rennigan, and finally the Sharingan
it's not known how the Sage got the Rennigan. It's highly unlikely he was born with it, and not to mention the rennigan bares a strong resemblance to the Juubi's eye. And you're just gonna tell me it's a coincidence that the man who defeated the Juubi just so happens to have eyes that resemble the beast's own eyes.
Take a look at that picture, it shows the sage fighting the Juubi, yet his face is not shown, probably to hide the fact that he did not have the Rennigan until after his battle.
not to mention in volume 64, Neji, who is of the Hyuga, stands in a VERY similar fashion to the sage.
The Juubi has been shown to be able to sprout trunks, flowers, leaves, roots & many other plant parts. This, combined with how the Juubi's eye looks like a Super Sharingan, makes me belive that, the Sage's children were born while the Juubi was still inside of him, this in turn gave his two children the power of the Juubi, the elder son gaining the Juubi's eyes, and the Younger the Juubi's body.
Now, by saying that the Uchiha & Senju powers came from the Juubi, where did the Hyuga & Uzumaki come from?
Well, I've already explaind my theory of how the Sage most likely had a Byakugan.
As for the Uzumaki part, please view this thread made by Sir Derp Obito:
It's possible, in a sense, that he had an Uzumaki body (Long Life) & Hyuga eyes (Byakugan).
whilst the Juubi had Senju Body (Wood Style) & Uchiha eyes(Sharingan).
This may explain why the Senju & Uchiha are stronger than the Uzumaki & Hyuga, as they have powers that were given to them by the Juubi.
I see the Uzumaki as the body powers for humans
and the Juubi Mokuton as the body powers for gods.
I see the Byakugan as the eye powers for humans
and the Juubi SharinganRinnegan as the eye powers for gods.
Some of you may say "LOL BYAKUGAN IZ FODERZ EYE TROLOLOL SHARINGAN & RENNIGAN MUCH BETTER!!!"
The byakugan is just a simple eye....at least when compared to the Rennigan & Sharingan. I believe the Rennigan & Sharingan are basically mutated Byakugnas that are infused with the Juubi's powers, which is why they have such crazy and powerful techniques.
The design itself of the byakugan is just so simple, it screams "basic". The eye is nothing but a blank iris and pupil. Nothing else.
Now add something to that blank, and you get a sharingan or a rinnegan. Thr byalugan almost looks like a "sketch" of the other two eyes.