Sorry if this is vague. Let me qualify.
- The civilization must have governed itself continuously. It can’t have been invaded and ruled by another group even for a short period of time.
- It must be fairly homogeneous in terms of ethnicity. The country must consist of a group who share a common heritage.
- It must have existed in the same geographic location. It can’t be the United States even though some of its citizens can trace their roots back to the Mayflower.
In the end, I’m looking for the group of people of earth who could claim to have the richest continuous heritage.
I’m thinking China or Greece or maybe Japan.