Board Thread:Theories and Speculation/@comment-1872728-20151008094957/@comment-2120712-20151008190317

Ninja Of War wrote: Actionmanrandell wrote: Sharingan91

there is no proof that anyone other than hashirama had ever had wood release. sure its called a kekkei genkai of the senju clan but any normal senju would never be able to even attempt wood release as it would instantly over power and kill them only asura's transmigrants have the required life force to use wood release so if anyone else had wood release than they were transmigrants True, but it is kinda hard to believe that something classified as a Kekkei genkai(Bloodline limit) is only available to one person in the history of the world naturally. Though it is just a theory, it does make a lot of sense as Kurama even stated that the ten-tails husk contains a lot of life force, enough to keep the former ten-tails jinchuriki from dying after the tailed beasts were extracted, so it's not too far-fetched to think that something like this is possible.

This might be just nothing but during the ten tails revival, Hashirama noticed that Madara was trying to force Obito to bring him back to life with the Outer Path — Samsara of Heavenly Life Technique, how did Hashirama have any knowledge of this technique and the rinnegan's abilities in the first place?

Maybe the Sage wanted to keep the descendants of Asura informed as well. Asura or Indra could of written down info about their father's abilities or at least passed the info down orally. Seeing as Hagoromo left one side of his descendants a Tablet with all kinds of info, he clearly did not want his descendants to be ignorant of the past.