Disbandment
The first Nuwaigans were migratory, spending long stretches traveling across the ocean, then temporarily settling in certain areas for a while, before moving on again. However, every time they stopped, there were going to be at least a few people who really liked where they were currently at and wanted to stay. And, due to how Nuwaigan genetics work, the more generations a group stays in one area, the more they become adapted for that environment and the less adapted they are for the traditional long distance voyages. So, during an era of time known as the Divergence, the settled populaces gradually began to outnumber the traditional voyaging populace, and the different Lineages emerged.