Genetic diversity shows you need need 50-500 people to maintain enough diversity to prevent gene drift and too much inbreeding
Social relationship. The number of relationships you can keep in your head is about 150 called the Dunbar number. The number is actually between 100-250. So surprisingly close.
Tribal relationships. The smallest size is 50 band and the clam size of 150. Across a wide variety of communities with the religious communities lasting longest.
Makes you wonder if we aren’t programmed to be tribal given the many years we lived on the savanna.