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David R. Samson is an associate professor of biological anthropology at the University of Toronto and the author of Our Tribal Future: How to Channel Our Foundational Human Instincts into a Force for Good.

For many, the word “tribalism” conjures images of racism and sectarian violence playing in a constant loop on the 24-hour news cycle, or leaders mobilizing their supporters by pitting the differences of one group against another in a zero-sum political game. All of these troubling elements are indeed related to tribalism, but you may be surprised to learn that its original evolutionary purpose, and primary function, was to bind strangers together.

At its core, tribalism is an intricate trust-signalling system. In a world with finite resources, knowing whom to trust – what organisms to invest energy toward – is the difference between life or death, reproduction or extinction. It’s one of the most ancient dilemmas of life on Earth. And in this regard, evolution has crafted several answers.

The first answer was simple: trust family. With the universal success of this solution, behaviours that privileged kin became written into the code of most life on Earth. But evolution didn’t stop there. The next solution, for brainy enough animals, was trust friends. Friendship was a radical innovation, and it serves as a kind of natural insurance policy against the unpredictability of life. But with its computational expenses, it too was limited in scope. As humans became one of the most successful animals on the planet, we scaled beyond the capacity for face-to-face relationships. Our success came back to haunt us; as we proliferated in droves, we became encroached upon by strangers. Humanity needed a new answer to the question.

The newest answer was trust tribe.

So what, then, is a tribe? Put simply, a tribe is a group that uses symbols to identify and signal membership. It communicates to strangers, “I am your ally, let’s co-operate.” It is a type of secret society, where the signals of coalitionary alliance serve as the “secret password” to gain the rights, responsibilities and benefits of the collective imagined order. If you pass the test, and you are treated with a positive bias by your fellow members, then you are bestowed with tribal identity and the host of privileges and responsibilities that come with it. No other species on the planet has this amazing capacity at its disposal.

How did our species develop this adaptation? Evidence suggests it was a gradual process. The first humans lived in camps of around 20 adults 1.8 million years ago. These “nuclear” camps were crucial for survival, serving as a joint effort to find food and provide mutual protection. But humans can’t sustain themselves in smaller groups, and so, from 1.8 million to 300,000 years ago we formed bands of about 150 people. These Paleolithic neighbourhoods functioned as resource exchange networks and protected against incest. Everyone knew each other by name, but living together was not a requirement.

The first tribe emerged 300,000 years ago, coinciding with the arrival of anatomically modern humans. The tribe as a social innovation was remarkably successful, resulting in the “social conquest of Earth.” Evidence of tribal signatures from this era supports this claim, such as the discovery of 45,000 non-local obsidian flakes in Kenya that were associated with the widespread use of pigment. The pigmented tools functioned as tribal signals, identifying the source people who crafted the material hundreds of kilometres away. This group of humans used symbolic colours to establish their identity on goods they traded with other groups. Whomever the humans were, they were among the first Earthlings to leverage the power of identity for collective action.

Let’s consider religion as another example of a powerful tribal signalling system. The earliest forms of religion, such as animism and totemism, were primarily used by small-scale societies and foragers to bond together in coalitions and eliminate competing ones. However, as humans began living in densely populated urban areas, these initial forms of religion failed to scale. To address this problem, humans evolved the concept of a moralizing god. These gods, who were believed to enforce a strict code of conduct and morality, allowed for the formation of large-scale societies and helped to promote co-operation among strangers. A recent analysis of 414 societies spanning the past 10,000 years across 30 regions around the world found that moralizing gods tended to follow, rather than precede, large increases in social complexity with populations of over a million people. While moralizing gods are not a prerequisite for social complexity, they appear to be a powerful tool for enforcing co-operation and promoting the growth of multitribal groups into super-tribes. As with political tribalism, moralizing gods allow for the centralization of power and the ability to enforce co-operation from the top down.

The “tribe drive,” this instinct to create and belong to coalitions using symbols, can be seen as a blessing. It increased co-operation within groups, which led to unparalleled human success and propelled our species across the planet. Yet, the blessing came with a terrible curse. The coalition instinct has also resulted in a tendency to conform and view outsiders as enemies. This can lead to extreme behaviours, including the dehumanization of other groups. This paradoxical result is the answer to a profound moral question about when it is acceptable to use violence versus when to apply the virtue of compassion.

Within a group, being compassionate and protecting one another is encouraged, but there is also permission to use violence against tyrants and freeloaders. Outside of the group, it is acceptable to be compassionate toward those who share identity signals that foster co-operation, but it is also acceptable to dehumanize and use violence against out-groups when resources are limited. Moral intuitions, such as those attached to religion, politics or any other ideological system that can be latched onto one’s personal identity, have evolved alongside the tribe drive and affect our daily lives.

At this point, it may seem tempting to wallow in fatalism and despair. If the tribe drive is an instinct, how can we possibly fight it? I remain optimistic, because science has uncovered the most effective way to reduce the pull and influence of instincts. To defeat an instinct, you must first be aware of its existence. Drives hold their greatest power over human behaviour when they remain imperceptible. Knowledge of our unconscious impulses is the key to preventing their manipulation of our individual and collective destiny. As science continues to unveil the mechanisms of this freshly discovered instinct, we can find mental keys to unlock the invisible shackles that confine us and ultimately improve our moral landscapes. Nothing less than the fate of our species is at stake.