Tribalism

When people have tried everything and have discovered that nothing works, they will tend to revert to what they know best—which will often be the tribe, the totem, or the taboo. Tribalism is a way of being, or a set of attitudes, associated with living in a small group of closely related people, with an implied cultural and ethnic uniformity. Many traditional tribes have referred to themselves using an meaning "people" or "human beings." Quite often they use less flattering language to describe groups of people outside the tribe.

In popular culture, tribalism connotes chauvinistic othering: the belief, or tendency to accept, that a group that includes you is superior or should be favored over other groups. Often this includes demonization of groups that are seen as opposed in some way, and a tendency to sympathize with people who share certain traits with you over those who do not.

While many in the Western world think tribalism is archaic, it remains a vital force in people's lives throughout the world, governing social conduct, political and militia alliances, and women's rights.

Islamic culture
Tribalism through arranged marriages to hold land became accepted practice in many Islamic societies. Islamic law intensely governs personal relationships, and the concept of corporations never developed. In the Western world, the concept of  developed to hold title for land held by churches whose stewardship passed to successive generations while ownership remained with the church. From this came the idea of a corporation, a collective perpetual entity with the legal rights of a person whose overseers hold responsibilites and not necessarily exclusive ownership rights. Under shariah no such corporate law exists other than rights to the holdings of mosques and religious property.

State formation
One theory of socio-political evolution suggests that tribalism comprised an intermediate step on the road of state formation - starting with family groups and moving through forming clans and tribes and chiefdoms and ending up with empires, nation-states and  federal conglomerates like Canada or Mexico. Take the idea with a grain of salt.

"Our" achievements
One aspect of tribalism that pops up in a variety of contexts is a tendency to try to share in the credit for the achievements of other members of a group with which one identifies, without having put in any of the work - most often by misusing the pronoun "we". This is a common occurrence in sports fans who say "We won" instead of "My preferred team won while I stared at the screen from my recliner". Interestingly, one doesn't hear "we lost" nearly as often.

Less innocuously, this "self-conflation with high achievers" phenomenon can also manifest in nationalism and national and cultural pride, when one gleans a feeling of personal superiority on account of others of the same nationality who have done a service to the country, or when one states that "we invented" something without actually having done so, on the basis that the inventor was of the same culture. A blatant example of this variant was provided by Donald Trump who boasted "We write symphonies"; we have yet to hear of his symphonic output. A quote by Arthur Schopenhauer, equally applicable to both cultural and racial pride, comes to mind: "The cheapest sort of pride is national pride; for if a man is proud of his own nation, it argues that he has no qualities of his own of which he can be proud; otherwise he would not have recourse to those which he shares with so many millions of his fellowmen."