To say that humans are tribal creatures is to say the single most culturally significant thing about us. Our sense of ourselves as social beings, grounded and shaped by our social context, is more psychologically important than our personal identity. As I argued in The Art of Belonging (2014), ‘Who am I?’ is never the real question for us; the real question – the most interesting and significant question – is: ‘Who are we?’

Yes, we need a sense of our individuality as well; to be reassured that I am who I am and no one else. But even our sense of personal identity is essentially social: if you want to find yourself, don’t gaze into a mirror or at your own navel; gaze instead into the faces of family, friends, neighbours and colleagues – the people who love you or at least are prepared to rub along with you. We discover who we are by discovering where we belong.

Like many other species on earth, we really do need each other to survive. We must congregate; we must cooperate; we must establish and maintain the communities that sustain us. A great deal of behaviour that might otherwise seem puzzling – our eagerness to conform to the social norms of a group, for instance – can be explained by that deep need to connect, to belong, to be taken seriously by others and accepted by them.

Some of our social identity derives from our membership of small, herd-sized groups – typically six to eight people – that satisfy our need for social intimacy. Herds can range from nuclear families to friendship circles, work groups, sporting teams, book clubs, musical ensembles and special interest groups of all kinds. But we also need to belong to larger and more muscular groupings: in addition to the emotional comfort of small groups, we need the strength, power and protection of the tribe.

Traditionally, extended families satisfied our tribal urge, and they still do for many people on the planet. But the stability and cohesiveness of extended families in Western society is breaking down in the wake of high divorce rates, low birthrates, an increasingly mobile population and a culture of rampant individualism. (There’s a potential counterrevolution in the new cyber-tribes of the internet, but we have yet to see whether digital connectedness will encourage the same kind of moral sensitivity and responsiveness as occurs in communities that rely on face-to-face encounters.)

Modern tribes take many forms. Some organisations generate a strong sense of tribalism – esprit de corps – among their employees, while also fostering strong links between the members of smaller work-group herds. Professional people such as doctors, dentists, lawyers and psychotherapists, who often work in isolation or in company with just one or two others, need the collegiality of professional associations and tribal gatherings (euphemistically called ‘conferences’).

Political parties operate like tribes – though there are often several factional sub-tribes within each party. Schools and, to a lesser extent, universities generate strong tribal identities fuelled by ‘school spirit’. There are socio-economic tribes in the various regions of our major cities; commercial tribes of people who strongly identify with particular brands; and cultural tribes based on shared tastes in the arts, shared convictions about social justice or a shared inclination to hang out in certain places.

Religion is one of history’s most obvious examples of how we satisfy our tribal yearnings, even potentially transcending ethnicity. Because religious faith and religious convictions run so deep, they foster intense feelings of belonging among groups of like-minded people, and that can work in both positive and negative ways.

The ‘in-group’ effect has a generally positive psychological impact, boosting people’s confidence and reinforcing their conviction that they are on the right side. ‘I’m a Christian’ or ‘I’m a Muslim’ or ‘I’m a Jew’ are statements that link people to vast global movements rich with cultural tradition. Within each of those tribes, though, there are sub-groups that sharpen people’s sense of identity and further strengthen their tribal bonds: ‘monolithic’ religions turns out, on closer inspection, to be far less monolithic than they may appear to outsiders. ‘I’m Catholic/Sunni/Orthodox’ carries even more emotional and cultural freight than ‘I’m a Christian/Muslim/Jew’.

While intense feelings of tribalism imbue us with a feeling of social and emotional strength, the downside is obvious: ‘in-groups’ beget prejudice against ‘out-groups’, often questioning their legitimacy and mocking their beliefs. The consequences of those divisions for social cohesiveness can be disastrous. (As the satirical novelist Jonathan Swift put it, ‘We have just enough religion to make us hate, but not enough to make us love one another.’)

Some of history’s most bitter religious hatreds have been between people who seem to outsiders to be closest to each other on the spectrum of faith: Protestant/Catholic and Sunni/Shiah struggles over hundreds of years testify to the destructive power of divisions between tribes-within-a-tribe. The fact that Anglicanism incorporates both Catholic and Protestant traditions almost guarantees that it will be riven by tribal conflict within its own walls. The broader the church, the less likely it is to remain cohesive.

Because we are by nature tribal beings, conformity comes naturally to us, but it doesn’t always bring out the best in us. People desperate to belong to a particular tribe may suppress their own convictions and their own sense of integrity in order to meet the expectations, mores, conventions and style of the tribe, and that can be psychologically damaging for them.

Part of the appeal of extreme or marginal sects and cults lies in their intensely tribal character: the former members of such groups often reflect on how much they felt they had had to give up to be accepted by the group and, in turn, how much they lost, emotionally and socially, when they decided to leave. (People in Glass Houses, Tanya Levin’s 2007 account of leaving Hillsong, is a graphic case in point.)

Nothing is more intense than the hatred directed at people who switch tribes: ‘turncoats’, ‘traitors’ and ‘backsliders’ are the kind of derogatory terms we reserve for those who have turned their back on our tribe.

Extracted from Beyond Belief: How we find meaning, with or without religion by Hugh Mackay. Available now, RRP $ 32.99, Macmillan Australia.