Human evolution primarily occurred in small hunter-gatherer groups, as opposed to in larger and more recently settled agricultural societies or civilizations.
With a negative connotation and in a political context, tribalism can also mean discriminatory behavior or attitudes towards out-groups, based on in-group loyalty.
The proverb "birds of a feather flock together" describes homophily,[1] the human tendency to form friendship networks with people of similar occupations, interests, and habits.
Other scholars argue that fictive kinship is common in human organizations, allowing non-kin members to collaborate in groups like fraternities.
Thus, groups with a strong sense of unity and identity can benefit from kin selection behaviour such as common property and shared resources.
[13] Dunbar's conclusion was that most human brains can really understand only an average of 150 individuals as fully developed, complex people.
[14][15] Malcolm Gladwell expanded on this conclusion sociologically in his book, The Tipping Point, where members of one of his types, Connectors, were successful by their larger-than-average number of close friendships and capacity for maintaining them, which tie together otherwise-unconnected social groups.
Once a person's limit for connection is reached, the human brain resorts to some combination of hierarchical schemes, stereotypes and other simplified models to understand so many people.
[23] The article was then republished with the title "Leadership and Professional Development: Specialty Silos in Medicine" along with an apology from the editor-in-chief.
[24] The revised version of the article substituted the terms groups and medical specialties for tribes, and siloed and factional for tribalism.