Dunbar’s Number was invented by British Anthropologist Robin Dunbar, who was able to determine how societies operated in prehistoric human culture. He found that by measuring the average human brain size and then taking from the results of other primates, he felt that humans could comfortably maintain roughly 150 stable relationships.
However, “relationships” did not necessarily mean close people in one’s life. The number of relationships you have for specific situations will be altered depending on the situation. How many people will you tell a major secret to? How many will you be comfortable crying around? The number shrinks as you begin to answer these questions. This is how we are able, as humans, to determine who we believe fit within our specific social groups.
There’s also a cognitive limit in relationships as well due to how tribes were formed. Roughly 150 to 250 people would be in some of the largest tribes. Meanwhile, smaller tribes were estimated to be between 5 and 20 people at a time. The latter could be the group that we consider our close or stable relationships while the former are those we’d consider friends. Basically, humans were never meant to be isolated or alone. Prehistoric to present-day data proves this