Dunbar’s Number: A Simple Summary

Dunbar’s Number

Humans, like all primates, are social animals with brains that have evolved to manage social relationships. Managing social relationships isn’t easy though. Our brains are only so big, so there’s a limit on how many relationships we can effectively manage.

In humans, the upper limit on the number of relationships we can manage is 150. This number is known as Dunbar’s number after the anthropologist, Robin Dunbar, who calculated it. It’s worth noting that the actual work he did involved a significant amount of extrapolation. He actually proposed quite a wide range for the number of relationships humans could manage. 150 is just the number that’s now used as the baseline.

Why Dunbar’s Number matters

From a work perspective, the implication of Dunbar’s number is that there is an upper limit on the size of any group that can work effectively together

Once a group gets to be larger than 150 people, then it’s impossible for everyone to know everyone else. Individual relationships break down. Since people don’t know each other in large groups, the usual methods or maintaining social relationships don’t work. New mechanisms are required to help the group work together effectively.

Most organizations implement hierarchical structures to enable larger groups to work together effectively. With these come rules, responsibilities, processes, ways of workings, values and behaviors and, ultimately, chains of command and authority enforced through control. In addition to these core tools, things like cultures, beliefs and customs also evolve to help larger groups work together towards achieving common goals.

Some organizations, though, have concluded that to function effectively all of their teams should be limited to 150 people. A frequently stated example of this is W.L. Gore Associates (of Gore-Tex fame) who are said to split any division that reaches 150 people into two smaller divisions.

The way we work together as groups is fascinating and hugely important for the success of our teams and organizations. This is brought to life through the need of teams to storm, form, norm and perform. It also affects our organizational cultures, employee engagement and wellbeing. Factors like social threats and psychological safety are shaped by our group dynamics.

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There is some dispute about this concept and the specific number. However, the underlying idea that people can only meaningfully manage a limited number of relationships is accepted.

It’s also clearly true that getting to know the people you work with improves working relationships and productivity. This is part of the reason the whole “team building” industry exists. Exactly what this means for work though, is a bit less clear.

It seems apparent that larger organizations require artificially implemented social structures (e.g. a hierarchy) as well as visions, missions, cultures and the like to work effectively. However, there are some indications that this is changing a bit. Some organization strive to be less hierarchical and more based on special teams that come together for specific delivery objectives.

Whatever you think of the number, remember that social relationship take some effort to maintain. If you’re an individual, take time to get to know those around you. If you’re a leader, it’s even more important that you try to invest in your relationships.

The information supporting this post comes from interpretations of Robin Dunbar’s work. You can read some of his original work in his article: “Neocortex size as a constraint on group size in primates” from the Journal of Human Evolution.

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