In discussing Dunbar’s Number and urban tribes, I’m looking for fundamental scales of human organization. Ryley pointed me to two quite similar hierarchies:

The military grouping is often said to be consistent throughout history, although with support units it’s hard to be sure apples are compared to apples. I think the numbers have been tending downward in the last 100 years due to area-effect weapons and mobilization (you can control less troops when they’re moving around really fast and you don’t want to keep them too close together). This guy claims that you need 6 people to maintain sentries, which might have something to do with why teams are almost always deployed at least in pairs (eg: one of my favourite video games, Full Spectrum Warrior).

“Support cliques” and “sympathy groups” are so named by Dunbar because of specific ways of measuring them: your support clique is your first line of support in really tough times and your sympathy group is the people who’d be devastated if you died. This table makes it clear that the phrase “urban tribes” was coined by Ethan Watters without much background reading. Watters is talking about post-kinship, post-economic families and needed a snappy name.

Anthropologists are convinced that these group sizes are based on human cognitive limits. I’m not sure I’m ready to give up my dedication to 8ish as a common human grouping (for example, as the maximum size for an ad-hoc meeting) given that 7±2 is the most famous human cognitive limit.

I recently read Urban Tribes: A Generation Redefines Friendship, Family, and Commitment by journalist Ethan Watters, which is expanded from a NYTimes article. The book doesn’t offer an explicit definition of “urban tribe”, instead is gives an ostensive definition in the form of a case study of Watters’ tribe and anecdotes about other tribes. I’d like to attempt a more explicit definition here.

An urban tribe is a group of friends with the following characteristics:

High clustering coefficient

In graph theory, clustering coefficient is a measure of how cliquey (that’s the technical term, I’m not making this up) a network is: the relationship between two members is similar to the relationship between any two other members. The most striking consequence of this is that urban tribes can contain pairs of members who don’t really like each other but still invite each other to tribe events.

Provides family functions

Traditionally, families fulfill a number of social functions besides raising children: entertainment, emotional intimacy, etc. Young adults used to live with their families until getting married. Now they move to cities while still single and are discouraged from marrying immediately. Urban tribes exist so single young adults can receive the benefit of families without getting married or living with their parents.

Homeostatic

Cybernetics generalized the concept of biological homeostasis to describe systems that adapt to maintain their integrity. Watters’ research begins with an attempt to explain the low marriage rates in his cohort, his striking conclusion is that urban tribes discourage long-term romantic relationships, especially with people outside the tribe. This is because members with a “real” family will have no need for the tribe. This isn’t a conscious action of individual members, but an emergent behaviour of the tribe attempting to survive.

Watters says most tribes have around 8 members, but it’s not clear if there are minimum or maximum sizes.