Redefining the division of times

The spread of D virus has caused hundreds of millions of destruction to mankind all over the world. The remaining humans have to reproduce and create new civilizations in the time after they survive at that time, the earth had no concept of state or regime. Instead, it was a more primitive concept of ethnic group. No matter what kind of people, no matter where they came from before the destruction, as long as you were judged to belong to that ethnic group, you will eventually start your legendary life in this ethnic group!