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

[YukikoKurosawa]

Supposedly Hydaelyn's sundering killed every single remaining Ancient, along with splitting their souls. They would then be reincarnated into various different races, presumably by her will. How, it's never explained. Something something creation magics. It's sort of dissapointing in a way, as it destroys any theories about the origins of certain races like Au'ra, we now know for certain they're not dragons (couldn't be since dragons are aliens) or demons, they're just giant humans sundered and reincarnated into dragon-girls. Even the beast tribes are reincarnated ancients based on the fact that the Sahagin priest from post-ARR had the echo. Well except for certain artificial ones like the Ixal which were created by the allagans, hence why they don't show up on the First.