An Eorzean Timeline.

[Anonymoose]

Could it be that we are all of Allagan descent?

I question it somewhat. Read the race biographies for Elezen and Hyur on the NA site. We're told that the Elezen were the sole inhabitants of Eorzea until the Hyur migrated in what was akin to invasion. The Hyur have been in Eorzea for a thousand years. That's nothing; the Sixth Astral Era alone was 1,572 years - and the Allag were destroyed in the Fourth.

There's a pretty good chance that all of the Allag were Elezen.