Would still like to know how mankind deviated into so many different variants

[Lauront]

Varis may be a biased source given he got his information from Emet and possibly Elidibus, both of whom refer to mankind after the sundering as "malformed creatures", but it's still all I've found in game about it thus far.

Good spot. At this point I've little reason to doubt their testimony on the matter (although I would suspect the "malformed" thing also refers to the state of the soul, which Emet at the very least could directly see, as well as their physical state.) I do wonder if they'll ever come back to this but it does strongly hint at it being a side-effect of the sundering.