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.

[ArcaviusGreyashe]

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

The fact there are tales about Azim creating Raens and Nhaama creating Xaela makes me think Azem (us, Venat or another one) created some familiars that became a species, and a Nhaam-something created Raen. Same for Azeyma being the guardian deity of seekers. MAYBE we'll have an hint in the next raid 24 about some ascian named Halona that created pointy ears familiars, who knows ?

If you adhere to the "allagans are just a lawful evil version of ancients", it's the same that happend with ixalions : they created a race (slave-race, in the case of ixalions) that became a species.

Every "human" race exist in all worlds, so they existed before the sundering. It's said allagans captured miqo'tes, so they did not create them, and G'raha only got allagan blood to prevent the Allagan technology to disappear entirely. Probably an enslaved race, again.

Plus, Venat could totally have created lalafells, since everything she creates is either fluffy, small, round, or a combination of those.

[Selvokaz]

The fact there are tales about Azim creating Raens and Nhaama creating Xaela makes me think Azem (us, Venat or another one) created some familiars that became a species, and a Nhaam-something created Raen. Same for Azeyma being the guardian deity of seekers. MAYBE we'll have an hint in the next raid 24 about some ascian named Halona that created pointy ears familiars, who knows ?

If you adhere to the "allagans are just a lawful evil version of ancients", it's the same that happend with ixalions : they created a race (slave-race, in the case of ixalions) that became a species.

Every "human" race exist in all worlds, so they existed before the sundering. It's said allagans captured miqo'tes, so they did not create them, and G'raha only got allagan blood to prevent the Allagan technology to disappear entirely. Probably an enslaved race, again.

Plus, Venat could totally have created lalafells, since everything she creates is either fluffy, small, round, or a combination of those.

This makes me think, in the case of Au'Ra, if you travelled back in time as an Au'Ra and word got around that all those observers you helped as the then-current Azem's familiar that he/she sent to Elpis was very knowledgable, wise, strong (for a familiar), and thus would like to have a similar one, it might make Azem decide to in fact create said race as a concept, hence you kind of give birth to yourself(race) type of situation lol. Wait it could be true of any race now that I think about it.

[ArcaviusGreyashe]

This makes me think, in the case of Au'Ra, if you travelled back in time as an Au'Ra and word got around that all those observers you helped as the then-current Azem's familiar that he/she sent to Elpis was very knowledgable, wise, strong (for a familiar), and thus would like to have a similar one, it might make Azem decide to in fact create said race as a concept, hence you kind of give birth to yourself(race) type of situation lol. Wait it could be true of any race now that I think about it.

Considering you're the strongest and most blessed of Hydaelyn's champions because you're the one she met and adored in Elpis, and that you were to Elpis in the first place because you were the strongest and most blessed of Hydaelyn's champions, we're already in a "give birth to yourself" mind loop xD

[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.

[Lauront]

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.

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.

Indeed. We can assume similarly of the Void from what we know of it. It's one of my slight disappointments with how they premised the differences of the First and Source, as these are worlds with differing aetheric densities (something the lore is not shy about emphasising as making a difference in outcomes, e.g. here, but also stated in EE vol1) and passage of time... but I suppose they really did just want to do a 1:1 to Eorzea on some level, but more high fantasy.

Even without the usual environmental pressures at play, mating choices alone should've resulted in some manner of speciation that is distinctive across each world, as this influences which traits propagate... but instead we have exactly the same division of races, right down to the clans. Perhaps it just doesn't operate on the same genetic principles as do RL life forms (i.e. for hybrids, traits defining the race cluster back together within a very small number of generations, perhaps even a single, and those influencing individual traits are not so much heritable as randomised within a pool available to a race and clan, or at least not as strongly heritable as with RL humans; combined, something like this would prevent prominent speciation based on mating choices persisting), which is not exactly inconsistent with many life forms being created through magic. Barring the possibility of creations/similar entities, even other stars appear to be mono-racial as well, which makes you wonder about how life originated on each star and what influenced its development. Both the ancients and dragons, for example, possess some very great powers innately.

With that said, for the time being we just have to roll with the fact that there's precious little difference between the assortment of races/species between each Reflection, barring anything that appeared post-Sundering, and assume they're just physical forms potentially created by the ancients, which the star saw fit to dump ancient souls into.

[Kakurady]

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.

Lore implies Hyurs (like real-world humans) are just really good at long-distance migrating.

In the character creation screen, it says Elezens regard themselves as native to Eorzea, while Hyur are said to have migrated to it from surrounding areas.

Of course, that having happened several eras ago, no-one in universe or out would know how reliable that is.