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The Dunbar number is a theoretical cognitive limit to the number of stable social relationships a person can maintain. It is typically cited as around 150.

It is relevant to thinking about the future of localism.

The concept was developed by British anthropologist Robin Dunbar, who discovered a correlation between the brain sizes of primates and the size of their social groups. Extrapolating this to humans, he suggested that the average person can maintain about 150 meaningful relationships – that is, people with whom you know well enough to keep in touch and care about their status within your social world.

Key Points:

• 150 is not a strict limit but an average; real-world numbers can vary (from around 100 to 250).
• The number applies to “stable” relationships – those involving regular contact and emotional closeness.
• The 150 limit is often cited in military units, company departments, and village sizes in traditional societies.
• Dunbar also proposed layers of relationship closeness:
  • 5 intimate friends (loved ones), 15 close friends50, 150 meaningful contacts, 500 acquaintances
  • 1500 people you can recognise

Why It Matters:

The Dunbar number has been influential in designing social networks, organisational theory, and community planning, especially in contexts like localism, where maintaining strong personal ties is vital for resilience and mutual support.

The Dunbar number aligns closely with the logic of localism, particularly as the economy contracts and social systems transition from formal, institutional structures to more informal, relationship-based ones.

Here’s how the Dunbar number supports the case for localism:

🔹 1. The scale of Community Life

Localism works best at the human scale – villages, neighbourhoods, or districts where people can recognise, trust, and support each other.

The Dunbar number (≈approximately 150) mirrors the size of traditional self-regulating communities, ranging from hunter-gatherer bands to pre-industrial parishes.

A local community of around 150–200 people enables mutual obligations, shared memory, and informal decision-making to flourish.

🔹 2. Governance and Trust

In systems where people know each other personally, enforcement of norms relies less on police or regulation and more on reputation and accountability.

Local governance becomes relational, not bureaucratic. The shrinking economy may favour this shift, as informal systems are less costly to maintain.

🔹 3. Design of Future Services

Local food production, shared child care, energy cooperatives, or health support networks (like neighbour-led care) all become more viable and resilient when grounded in groups small enough to be cohesive.

Dunbar-sized groups can self-organise using common sense and shared values rather than top-down management.

🔹 4. Rebuilding Social Capital

Modern life has eroded meaningful relationships. The transition to localism presents an opportunity to reweave the social fabric based on what humans are cognitively and emotionally equipped to handle.

When economies no longer offer purpose through jobs and consumption, relationships become the primary currency of well-being – and Dunbar’s number defines their natural limits.

🔹 5. Application in Design and Planning

New settlements or restructured towns could be organised in clusters of ≈150 people, with local governance councils, shared gardens, and communal spaces.

Rather than thinking in abstract zoning categories, planners could begin with the question:

In many ways, the Dunbar number is the natural unit of localism. It defines a scale at which social systems become personal. Within a group of 150, reputation matters. Kindness is remembered. Selfishness is noticed. Mutual help thrives. Formal institutions become unnecessary because people enforce social norms through personal relationships rather than relying on regulation.

Modern society has outgrown this scale. Services are remote, housing is anonymous, and people make decisions we’ll never meet. However, as the formal economy contracts and public services weaken, we may find ourselves returning to the older, more human-sized structures that our minds and hearts are built for.

Designing future settlements, neighbourhoods, or service hubs around this scale could bring profound benefits. Shared child care, neighbourly support for older people, communal gardens, food production, and even dispute resolution become feasible without bureaucracy. The Dunbar number provides a biological foundation for rebuilding localism – not as a nostalgic dream but as a practical necessity in a shrinking economy.

The lesson is clear: if we are to live within nature’s limits, we must also live within our own.