The limits of human potential is an important thing to know. Imagine if we didn't know our limit for breathing underwater. A lot of us would die. Or, imagine if we didn't know we could fly. Good luck with that, Amelia.
One limit that is uncommon to know if how many relationships we can carry at one time. 150. No matter what you believe about the human capacity or relationships, a community above the size of 150 people is inefficient. This has been tested time and time again and was even practiced by people who didn't know why it worked.
The Rule of the 150 was given by Malcolm Gladwell in Tipping Point, but is based on Dunbar's Number. Richard Dunbar, a British Anthropologist who studied the size of primates brains, saw a correlation with how many relationships it was able to carry.
Through careful research, Dunbar was able to determine that humans are able to maintain 150 stable relationships. Groups that are larger than 150 require more strict and enforced rules, less leeway when it comes to breaking those rules, and a decline in all-around productivity.
Gore Associates, a multimillion-dollar private tech company believes in the rule so much that whenever employment reaches 150 in a factory, a new factory opens. Half of the employees that worked at the old factory move to the new one and the cycle continues.
The most interesting thing about how Gore Associates operates is that no one told them that number, they didn't have any business consulting or third-party leadership knowledge. They simply saw that whenever that number was above 150, productivity decreased and profits were lost.
Gladwell, Malcolm. The Tipping Point: How Little Things Can Make a Big Difference. Boston: Little, Brown, 2000. Print.