Timeline
Remaining Tribes Migrate To The Southern Mainland
When it was decided, after much conflict, to yet again leave this new home they had made for themselves, the division between them lead to two different groups leaving the islands with two different headings. One of those groups set sail towards the South, finding the Vanamir mainland. These people spread out across this mainland over the course of several decades. While the mainland held more stable terrain, it was still not stable enough to support larger villages. Many of these settlements died out, not due to the sinking of their settlements, but rather due to an inability to adapt their agriculture methods successfully to the land.
Consolidation In The West
After many of the settlements built upon the Vanamir died out, many of the remaining population migrated towards the west. The colder climate in the west made for a firmer ground, allowed for larger settlements to grow. Over time, this lead to the population being almost entirely consolidated in the furthest west portion of the mainland.