well, it's strongly implied that it's PC in origin. AFOS says it was left by the people who made humans, to make sure humans were nice and sweet before they hit the stars. In previous shows, we know that humans were engineed by the protoculture. So while it's not spelled out, it's a pretty clearly implied relationship. And while you're right, there could have been further or earlier genetic tinkering by someone/thing else other than protoculture... well, there's absolutely no evidence to support that claim. Nor does it makes sense from a story telling perspective. Why lay down all this mythology and background and then suddenly come in and change it all? It makes more sense to continue to develop what was already started, what has been explored in SDFM, DYRL and M7.
Also, very little of PC's technology has actually been seen, and since they were masters of genetic manipulation, it's not unreasonable that their technology would have a very organic feel.