Human behavior can only be fully understood by studying the relationship between instinct, culture, social structure and economics.
The term instinct describes any unlearned behavior triggered by an environmental variable. Such behaviors are survival adaptations. They exist and persist because they statistically improve survival rate.
The instincts of social animals are adaptations which link individual survival to the success of a group. The authority, conformity, reciprocity, and pack instincts always express themselves in one form or another. Among humans, culture, social structure and economic paradigm determine how these instincts are expressed.
Homo sapiens sapiens is a social animal. Tribe: the human analogue of a pack. The sense of belonging is a fundamental human need. When that need is not met, replacements always emerge. Political partisanship, gangs, nationalism, cults, religions, even team sports… all are expressions of the same psychology — the tribal instinct.
The authority instinct increases the survival rate of groups by facilitating decisive action. This pattern is ubiquitous among social species. Presidents, warlords, gang leaders and chiefs are all human analogues of the alpha.
Humans have the tendency to emulate the thoughts and behaviors of their peers. Social conformity increases survival rate by facilitating group cohesion and coordination. The conformity instinct is triggered anytime there is the perception of group consensus, or social momentum.
When given a gift humans are instinctually incined to reciprocate. Among social species cooperative exchange facilitates the distribution of effort and resources within a group, and provides a natural safety net. At the civilization scale, the reciprocity instinct has been translated to debt and monetary systems. Repayment of debt is framed as moral duty even if the gift is artificial
Those who initiate conflict invite a forceful response. Those who do not retaliate when attacked invite further aggression. Both initiations of violence and passive responses reduce survival rate on average. Tit for tat is a mathematically consistent selective pressure. The retaliation instinct is a biological adaptation to that pressure. This is why every human culture has some concept of the right to self defense, and aggressive behavior is condemned.