Why human fight each other?

Answer 1

Because of sin.

_____________

From a Religion & Spirituality point of view, sin may be an adequate answer, but adhering to that answer will inevitably lead to strong sectarianism and to religious wars, which of course will be caused by righteousness and not by sin, not much of a step up. The results will be the same if not worse.

A more useful answer may be that humans engage in war because conflict and combat are part of human nature. There will be conflicts over borders, the distribution of scarse resources, cultural differences-- religion among the more important ones, struggles over international hegemony and lusting after power, exploitation of poorer or less developed countries that have a wealth of Natural Resources that are globally valuable, and there are probably many others. As long as there are humans that have not been blasted away by other humans, there will be conflict, and it will occasionally rise to the level of combat/war. Among the things that will help minimize such combat will be a strong sense of international interdependence espoused by groups like the United Nations.

Answer 2

Humans may fight each other due to various reasons such as differences in beliefs, power struggles, competition for resources, or misunderstandings. These conflicts may stem from a combination of factors including fear, insecurity, anger, or a desire for control. Ultimately, the reasons for human conflicts are complex and can vary greatly depending on the circumstances.

Answer 3

It is a holdover from the early days of man when fighting literally meant survival. The need may not exist anymore, but the urge is built in.