“We hold these truths to be self-evident, that all men are created equal”, declared the signatories of the American Declaration of Independence, but the slave-owning Thomas Jefferson did not seem to think they need stay that way. Indeed, if there’s one characteristic shared by almost every human society, it is inequality: the existence of a social hierarchy.
Humans aren’t alone in that. But in an ant society, at least you know where you stand: you’re either a queen, a worker, or a male, fit for nothing but reproducing. Humans, in contrast, have complex, many-tiered and overlapping hierarchical structures: only we seem to have developed the exquisitely nuanced caste of the local government officer. And though some might dream of utopias in which no one has any more power or importance than another, these social hierarchies always rear their head eventually.
Is this, in fact, a law of nature? A paper in the Journal of Theoretical Biology by economist Tamas David-Barrett of Birkbeck College in London and anthropologist Robin Dunbar of Oxford University seems to say so. It shows that the existence of a social hierarchy in a community can be adaptive, in the sense that it helps the community to function more efficiently. That’s because the hierarchy can make it easier for any individual to get hold of useful, reliable information – where to find food, say, or how to get a plumber – without having to ask everyone.
One can say that the social hierarchy of ants is rather flat – every worker ant is like any other in social rank, amount of knowledge and so forth – while that of humans is generally both steep (with a strong differentiation of individuals) and many-layered. We’re not unique in having several embedded layers of structure – other primates, elephants and orcas do too. Like us, they split up into subgroups – but like us, these aren’t simply little communities isolated from one another, but are interwoven networks in which individuals form and maintain social links.
It’s within this network that the hierarchy is expressed. That needs little explanation: we’re all familiar with, and probably guilty of, the impulse to derive status from proximity to power – or these days, to celebrity. “I went to school with Bill Gates”, or “My cousin married a baron”, or “I once played in a band that supported U2.” Considered as an aspect of biological or cultural evolution, however, the network should serve a rather more well defined and valuable function if it is to develop and survive. After all, elephants, so far as we know, don’t have a celebrity culture.
David-Barrett and Dunbar propose that these hierarchical social networks facilitate the dispersal of useful information in communities that need to coordinate their behaviour – all looking for food in the same place, say – but which are too big for everyone to consult everyone else. They have devised a mathematical description of that task in which a community of agents is interconnected by social links between individuals, each of whom consults its own personal network in one-to-one interactions to make a decision. It doesn’t matter what exactly the decision is; in the model it’s represented simply as a choice of which direction to face. The question is how long it takes the whole community to coordinate their individual choices this way.
If everyone in the network is equivalent – there is no social hierarchy – then there’s an optimal size both of the whole community and of one’s personal network that allows group coordination to be reached most quickly.