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1st Floor Lona House
212 Upper Buitengracht
Bo Kaap, Cape Town, 8001

Jaime-Lee Gardner
072 171 1979

Louise Martin
073 335 4084

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Size counts

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Size counts

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4 min read

One of the main reasons people move into residential estates is to recreate the sense of community typical of villages or small, well-defined suburbs. People knew their neighbours – and their neighbours’ pets – and they memorised each other’s phone numbers. In their heads! Kids played in the street or in public open space, wandered in and out of each other’s houses, and only came home when they were hungry.

There are still communities like this, and some estates approximate that halcyon era. But what is it that made villages work, and that can turn a residential community into a real community? There are lots of theories, but the most convincing is that proposed by British evolutionary anthropologist Robin Dunbar. While studying apes and monkeys, Dunbar noticed that specific species of primates had pretty much the same troop size, regardless of their environment. If the troop started to get too big, it would split, and a splinter group would leave to start up somewhere else. He guessed he was onto something there – something that would affect humans as well as monkeys – so he tried to work out the connection. Eventually, he figured out that troop size was governed by the number of individuals that each member could keep track of – and that was determined by the size of their neocortex. If that was the case, he reckoned, he should be able to work out the ideal size of a human ‘troop,’ and he did. It’s about 148, so let’s say 150.

The reason for this, Dunbar postulated, is that we can remember 150 people, we can relate to them personally, and we can remember the relationships between them. Community is all about trust – and you can’t trust people if you don’t know them. So it’s not a coincidence that many groups throughout history have numbered close to this magic number. From the Neolithic through to the 18th century, most villages had between 100 and 200 residents, most armies have companies of between 100 and 180 soldiers, and most church congregations fit in there too.

Once a community gets bigger, it becomes impossible to self-regulate just by peer pressure, so we need hierarchies, bosses and police. We need a structure to replace the informal structure that we could hold in our heads when the community was smaller.

It’s not a ‘rule’ and it’s not written in stone anywhere – it usually just happens. Think about it: everything is going smoothly, the village (church group/ division/whatever) is harmonious, and people are drawn to join, so it gets bigger. And then a bit bigger, but then, once it exceeds that magic number, people start rubbing up against each other. Disagreements are not dealt with as efficiently as before, and rival cliques start to form, until one of those cliques stomps off in disgust, or is expelled from the group. And we’re back to that happy number.

The people of the Maring region of Papua New Guinea practise a seemingly bizarre cycle of warfare and truce that, considering Dunbar’s number, makes a lot of sense. When the village pig population becomes too big to handle easily, tensions form, and relationships take strain. And this usually happens at about 150 to 180 pigs, which correlates to about 160 to 200 people. So the villagers decide it’s time to cull the adult pigs, but this ritual is tied in with warfare. So they send a signal to their ‘enemy’ neighbouring tribes, by cutting down their specially planted rumbim (or truce) trees. The neighbours see this so both sides start preparing for war. Over a period of about a year, they slaughter all the adult pigs, offering them to their ancestors and – possibly even more importantly – feeding the meat to their allies at glorious feasts to reinforce allegiances, and thus maximise their chance of victory. And then it all ends in one big rumble in the jungle, in which many people die. The surviving warriors plant a new crop of rumbim trees, to maintain a truce as long as they stand, and the cycle continues. It may not be the most pleasant way to limit the size of a community, but it works.

And, even though it does ‘just happen’, it can become more stringent. Almost all armies, for example, have a basic company size of between 120 and 180, and organisations ranging from Fortune 500 companies to relatively obscure religions have formalised the principle, pre-empting Dunbar by years or even centuries.

The highly successful and profitable company, W. L. Gore and Associates, that makes Gore-Tex, is organised around divisions of no more than 150 employees. There are 150 parking spaces for each division and, when there is no more parking, they split the division. Every single employee is an ‘associate’ with the same size and style of office, and there is no hierarchy, because none is needed – everyone knows everyone, they stroll into each other’s offices, and they discuss strategies or the progress of orders around the water cooler or in the tea room.

The Hutterites, a radical reformist protestant faith group that dates back to the 16th century, is organised into numerous small colonies. They are a self-disciplining community with extensive communal assets, so it is important that they avoid conflict. And – you guessed it – when a colony starts creeping over 150 people, ‘pioneers’ branch out and start a new one. But, because this is an acknowledged formalised principle, they usually don’t wait for dissatisfaction and disharmony to creep in, and so the new settlement retains a good relationship with its parent village.

Of course, an estate with only 150 residents is economically unfeasible, but developers and HOAs can use this knowledge by, for example, encouraging ‘sub-populations’ of park runners, golfers, bird-watchers or tennis players. Or building in smaller clusters with communal spaces that replicate the time-honoured village well, village green, market square, or some form of recognised community focus. Dunbar noticed that group cohesion is proportional to the amount of time members spend doing things together – and that includes gossiping. Sports facilities, jogging trails, central picnic areas, and swimming or boating dams encourage interaction, so – hardly surprisingly – the more possible activities and potential informal groupings an estate can offer, the happier the residents will be.

Actually, there are six Dunbar numbers, but 150 is the best known and – in many ways – the most important. The others are: five – really close intimate friends (or family); 15 – close friends; 50 – circle of friends, the people you may invite to a party; 150 we’ve dealt with; 500 – acquaintances; and, Dunbar postulates, 1,500 is the maximum number of people you can recognise and put a name to. So, no, your 3,427 Facebook friends are not really friends.

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