Board Thread:Theories and Speculation/@comment-1512913-20160329065033/@comment-734582-20160404082054

Georgio722 wrote: This makes more sense: The thing is, the Asura line has all sorts of weird abilities that make them ideal Senjutsu users and ideal Jinchuriki. The only natural users of Wood Release are Hashirama and the Juubi. The Uzumaki have natural sealing abilities, strong lifeforce and a natural ability to be Jinchuriki even of Kurama. Orochimaru's senjutsu curse seals were only compatible with 1 in 10 people, yet Naruto never had a problem with it. Hashirama too has Sage Mode, without animal markings.

The Juubi's power is natural energy, which can actually explains Hashirama's inexplicable Sage Mode. It explains why he has Wood Release and only he. And since the Juubi is all Biju combined, it even can explain why the Senju were so adept at so many jutsu, having a body that was naturally used to all these releases and abilities.