Here is a summary of Robin Dunbar’s [4] numbers and a video on how it has influenced the teams John works with.
The first and most well-known Dunbar number is 150, often referred to as Dunbar’s Number. It suggests that humans can maintain stable social relationships with about 150 individuals. These relationships are typically characterised by regular contact, personal knowledge, and some level of emotional connection.
Dunbar’s Layers: Beyond the 150 limit, Dunbar proposed the existence of additional layers, each representing different levels of relationship depth. The layers include 50, 15, and 5. The 50 layer consists of close friends and family members with whom individuals maintain more intimate connections. The 15 layer comprises best friends or close confidants, while the 5 layer represents the closest and most trusted inner circle.
These numbers provide insights into the cognitive constraints of human social networks. They suggest that our capacity for maintaining meaningful relationships is limited by our brain’s computational capabilities.
In our work, our default team composition begins with 7 persons plus-minus 2. Our strategy teams range from 15-60 persons. The Dunbar numbers are very helpful but are approximations. The key is to continually review team size and composition so each member has clarity, autonomy and engagement.
Understanding the Dunbar numbers can have implications for leadership structures, community building, and maintaining social connections. It highlights the importance of prioritising and investing in relationships, as well as recognising the limitations of human capacity for maintaining large social networks.
- Dunbar layers and numbers show the average limits of human social connections and intimate relationships (approximations, vary per person).
- Team size is intentionally kept at 5–9 people (7 ± 2) for effective relational flow.
- The Formula shows: more people = more possible connections, but too many leads to relational breakdown.
Cultural dynamics matter:
- In the Global South, people are often less assertive.
- Younger members may defer to older ones.
- Women may be quieter around men.
- Team practice: the youngest or the woman speaks first in meetings; in multicultural contexts,
- non-native English speakers contribute first.
- This ensures all voices are heard, not just the most articulate.
- Dunbar’s numbers help avoid over-expanding teams, preventing diminished connection.
4. Dunbar, R. I. M. (1992). Neocortex size as a constraint on group size in primates. Journal of Human Evolution, 22(6), 469-493. doi: 10.1016/0047-2484(92)90081-J.