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

[Selvokaz]

For every playable race, they are all still supposedly variants of mankind that came about after the sundering, or are some of them concepts created by the ancient humans? How does this work?

[Jandor]

We don't really know. Two main schools of thought seem to be:

The various races are just what happens when you split the Ancients 14 ways.

The concepts existed before and they're the new life Zodiark seeded.

[Gemina]

For every playable race, they are all still supposedly variants of mankind that came about after the sundering, or are some of them concepts created by the ancient humans? How does this work?

The playable races aren't the only humanoid creatures that qualify. The Padjal and Lupin for example. Even though the Padjal are just Hyurs chosen by the elementals to basically embody their will; they do still count.

The races almost seem like the features of the Ancients were divided and disseminated amongst the current residents. Tall stature going to Elezen and Roegedan; appearance to Hyur, Viera and Mi'qote; longevity to Padjal; beastly nature in their creations going to Au ra and Hrothgar. All the crud left over went into Lalafel. Kidding... kind of.

[Yuella]

https://en.wikipedia.org/wiki/Speciation

[Lurina]

The Doylist answer is that the writers, like a lot of stuff associated with the Sundering, probably just didn't want to create a definitive answer. Any clarification about the specifics of what "mankind" is in the modern day and how it diversified from basically just humans would lead to some uncomfortable questions about the ethics of what took place, and put some weird ideas in player's heads about the racial politics of the setting without doing anything to compliment the themes they had in mind.

For a Watsonian answer, you could reasonably guess that the Hyur and maybe the Elezen are directly descended from Sundered Ancients, while the other races are descended from creations or are genetic spinoffs. Aside from being visually the most similar, in the Elpis MSQ, an Ancient comments on the attributes of your race compared to their own, and the only remark Hyur and Elezen get is that their aether is really thin, while others are singled out for their bestial and unusual features. And the Au Ra backstory makes it almost explicit that they, at least, were created by the rival sides of the Zodiark vs Hydaelyn conflict.

The Hyur are also omnipresent across the entire planet in a way the other races are not, including in the New World, which seems to indicate them previously having been the dominant species of the world. Though, that's of course a post-hoc justification. The real reason is that they're fantasy humans, and making fantasy humans the generic race that's everywhere is just a thing writers do.

https://en.wikipedia.org/wiki/Speciation

The issue with this explanation is: Why would the races diverge in exactly the same way in both the Source and the First, when everything else about their timelines went differently? Any explanation has to be something which can be attributed to the moment of the Sundering, not afterwards.

[KageTokage]

I feel like there might be some light shed on this in the EW Alliance raids as we'd by necessity have delve into some of the world's earliest post-Sundering history to learn the truth of how the Twelve and related deities came to be.

[Selvokaz]

of course, there could be other races that are considered a part of mankind and or were once ancients, I mean Emet Selch chose to be a Garlean presumably, and im really at a loss for how the Garleans even fit into this. If you some how manipulated several generations of pairings between members of each mankind inclusive race would you eventually end up with an offspring that resembled the Ancients?

[KageTokage]

I feel like the Ancients in Elpis wouldn't have considered the non-Hyur races unusual (Who are immediately assumed to be familiars by their physical traits) if there were other races of man at the time.

I also think there was some kind of genetic manipulation/experimentation going on with Solus/Emet's line that we might end up learning about in the future.

[Vyrerus]

Without really knowing, I chock it up to being a side effect of The Sundering. Pure speculation ahead.

As the aether became relatively thin, compared to Pre-Sundering, Dynamis concentrations in the body skyrocketed. Leading to partial transformations based on positive emotions. This altered physical characteristics perhaps based on personal abilities or affinity for certain animals.

Think about Meteion's appearance. It's easy to describe as a humanoid bird girl. She's got wings for ears and taloned feet, but human everything else. It could have also been just unintentional. Whatever magick went into the Sundering may have influenced the change based on what was in Hydaelyn's mind, as that sort of thing affects all creation magic or anything similar. While it was transformative rather than creational, it's even more likely than my first supposing. Especially if Venat met a WoL who was a Viera/Miqote/Hrothgar/Au Ra.

Those are the only ideas I've got. I would like for them to expound on that facet of the game, but I think it's something they'll shy away from as well.

[kaynide]

There is also potential that some races were specifically created by the Allagan, such as how they created the Ixal. (Or at least created the Ixal by modifying an existing creature).

Seeing as how G’raha carries Allagan blood in his veins even though he is not an Allagan “man” it could be possible.

That said this is not supported as these races exist on the first. So unless the Ronkans did the same thing, or the Allagans could plane shift this is not a solid theory.

..that said there doesn’t seem to be any 3rd eye Garlean types on the first..so maybe they were created by the Allagan.