Board Thread:Theories and Speculation/@comment-1512913-20150520114510/@comment-4912646-20150521003451

I assumed that the substance the White Zetsu were originally made from and the substance that formed the Hashirama-clone-tree were essentially the same thing, since both are created by the Shinju or its lesser form. So basically... The databook also says the White Zetsu can transform into others because they can essentially be dyed any colour, so maybe that applies to their genetic makeup as well.
 * The Shinju transforms the humans it assimilates into sentient plant-men made out of white matter.
 * Hashirama's DNA cultivated by the Shinju's chakra (or rather the Demonic Statue's chakra) produces a non-sentient clone of him made out of the same type of white matter, except now it contains Hashirama's power and Wood Release.

On a related note, the identical White Zetsu that fought in the war referred to (what was later revealed to be) just one of many White Zetsu as the "original". We know that particular White Zetsu is able to create actual biological clones of himself that can exist independently, so are we to assume that all of the war Zetsu were just his parasite clones rather than transformed people? The databook even mentions something about the White Zetsu propagating using the statue's chakra, so it seems possible. But then that raises the question of where all of the unique White Zetsu went off to, aside from the "original" and Tobi.

The White Zetsu feel like one of the least properly explained things in this manga, alongside Obito's time in the Bloody Mist and the will materialisation ability. It's such a shame the databook didn't really clear any of this up after we waited years for it.