An Eorzean Timeline.

[NoloeTazier]

But is it not true that the miqo'te came over the frozen seas during a previous umbral era? If the hyurs were the first immigrants to Eorzea, certainly they must have do so well before 1000 years ago, at least before the miqo'te migration.

The Hyur are actually the newest race to Eorzea. When the first Hyur appeared in Eorzea, Ishgard was being founded. The Miqo'te came over in the Fifth Umbral era when the seas were frozen, 1500+ years ago. Nonetheless the Hyur and Elezen clashed, there's no wars reported until the Autumn War almost 1000 years later since the first Hyur stepped foot on Eorzea.

Essentially I think it looks like this:
Elezen -> Hellsguard Roegadyn -> Lalafell -> Sea Wolf Roegadyn -> Miqo'te -> Hyur.

Reason why I separate the Hellsguard and Sea Wolf Roegs is because the Hellsguard Roegadyn seem to have established themselves in the mountains of the north and learned the ways of magic, which I assume would take years and years of work and practice for a non-magical race to just learn the basics of magic. While the Sea Wolf Roegydan are simple Pirates and would have only chosen to live in Eorzea after (or during) Limsa Lominsa was founded.

I assume Lalafell have been in Eorzea BEFORE the seas flooded over because Shatotto and the Thaumaturge were already established in Eorzea when she created the Stardust Rod. Also Plainsfolk Lalafell loved to farm the soil on Vylbrand so I have to assume Limsa Lominsa is established as well...possibly by the Lalafell ships? Elezen established Gridania, Lalafell established Ul'dah, and Lalafell established Limsa? Limsa Lominsa was probably a collective of Roegydan and Lalafell.

Edit: Which actually brings up a huge question for me. The Archons are suppose to be reincarnated Twelve, Thancred is a member of the youngest Eorzean race the Hyurs. Louisoix and Urianger are Elezen and Elezen have long life spans than the other races of course for them to be 1500+ years old and have caused the Sixth Umbral era seems a little farfetched. But this is a time in Eorzea when Hyur are nowhere to be seen. So we're looking at Thancred and Yda..2 Hyur who's race has only been in Eorzea at the longest for 1000 years. If the Archons are reincarnated over and over as the same person, just a speculative example being Louisoix as the new silver-haired Elezen boy, how could 2 Hyur become Archons. So the 'real' reincarnation has to be: The Circle of Knowing choose the next reincarnated person or the Twelve's "soul" itself is born again in a new body regardless of the race.