Board Thread:Theories and Speculation/@comment-24824859-20160108012905/@comment-732150-20160108013341

The technology clearly exists, based on how Hashirama's Wood Release spread around. For the "many unrelated users with same kekkei genkai" situation, I think the most likely explanation is that they share an common ancestor. Shinobi that had these in the past simply didn't stick together like some clans, and when the hidden village system came about, they ended up in different villages. There's also always the possibility that they were actively "poached" from other villages, Kumo blatantly tried getting stuff from Konoha more than once, it wouldn't really be surprising if this was more common between villages than actually shown in the series.