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Who the heck is Robin Dunbar??

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Welcome to AKF Partner’s continuing series on notable personalities that impact business and technology. Today we ask… Who the heck is Robin Dunbar??

Robin Dunbar is a British anthropologist who in the 1990s found a correlation between primate brain size and the size of the primate’s average social group. Primates in the wild express a highly social nature. They maintain a very close personal contact with other members of their social group, usually through daily social grooming. These tight-knit social groups function as protective cliques within the larger physical groups in which the primates live. The number of social groups a primate can track and maintain appears to be limited by the size of their neocortex.

Dunbar used his observations of primates to suggest a theoretical social group size for humans; he arrived at a “mean group size” of ~150. Dunbar’s further surveys of villages and tribe sizes also appeared to approximate this “mean group size” at 150, but only for communities with a very high incentive to remain together. The group required a commitment to physical proximity and protection, as well as dependence on one another for subsistence. Consider, if you will, a village or a small town with 120-150 citizens.

Consider your own interpersonal relationships. Your family, close friends, business associates, and your acquaintances. Humans maintain a very close intimate relationship with only a small few others; our interactions with our acquaintances are either purpose-driven or surface level conversations.

How does Dunbar’s theory apply to determining Team Size in a modern software Product organization?

While corporate teams do not usually depend on one another for subsistence or for protection, they DO depend on one another to get their work done. A software engineering team may rely on services and data provided by other teams. They surely depend on a technology team to provide the infrastructure on which their software resides and runs for their customers. That engineering team also depends on the productivity and participation of its members to complete its goals. But how large can such a team be and remain successful?

A second consideration arises from Mel Conway who stated that “…each individual must have at most one superior and at most approximately seven subordinates.”

A team of 4 people entails 6 lines of communication, one line from each individual to every other member of the team. A team of 6 entails 15 lines of communication, a team of 10 entails 45 lines of communication.

Look for AKF’s short video about “Who is Mel Conway.”

One can mathematically describe this phenomenon where N is the number of people within a team, and the number of lines of communication is calculated as N times N minus 1 divided by 2. As the number of team members grows, the amount of time spent coordinating activities with the rest of the team increases. With very large teams more time is spent coordinating than working. There is, then a theoretical tipping point where a team becomes too large to remain productive.

Combining these thoughts and theories from Dunbar and Conway together, we arrive at an optimal team size of no more than 12-15 people. We see this naturally borne out in sports teams like American football, soccer, and baseball. We also see it in military units or squads, and anywhere concise communication is required for the proper functioning of a team. Smaller teams, focused on common goals and in close proximity to each other, benefit from natural human connection with all the verbal and non-verbal cues. Just like a small network within one building, co-located teams communicate with low latency. Big teams, particularly when dispersed over distances and time zones, must deal with slower, more challenging communication.

From a practical sense, that brings us to the conclusion popularized by Jeff Bezos at Amazon: “If you can’t feed a meeting with two pizzas, it’s too large.”

Consider 2 large pizzas (you imagine your own toppings) each sliced into 16 pieces. If each person were to eat 2 pieces of pizza, you could feed 16 people; if each ate 3 pieces of pizza, you could feed a team of 10 (with some left over).

Team Size – Key Takeaway

1. Elite teams should be small – no larger than 12 to 15 people.

2. High-functioning teams operate best when located in close proximity to one another

At AKF Partners, we have discussions on team size with our clients regularly. If you have questions about structuring YOUR organization using these and other principles, invite us in. You can find us on the web at We’d love to help!

Next Edition: Who the Heck is Fred Brooks??


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