"Humans are often said to be intensely tribal. Indeed we are. But if “tribal” refers to a sense of solidarity with a large social group, the same is true of most primates. Tribalism does not distinguish us, nor does reactive aggression. It is coalitionary proactive aggression that makes our species and societies truly unusual.
Among our ancestors, coalitionary proactive violence directed at members of their own social groups enabled self-domestication and the evolution of the moral senses. Now it enables the functioning of states."
(Richard Wrangham: The Goodness Paradox: How Evolution Made Us Both More and Less Violent)
I can easily relate to solidarity in the face of physical attack. I'm not half as sure about ideological solidarity. Maybe it needs to be fleshed out as to what the benefits and the disadvantages are. It's weird how it's a bit like a new civil war in America these days.
Interesting, you may find this a good read too.
The only thing that the two do not address, which I think comes into the picture, though I have nothing more than hunch, is the effects that weapon technology has on aggression. Making inter group aggression both more dangerous to the aggressor and more likely to result in the deaths of near relatives with common genes.
We are indeed tribal animals. But not all human groups practice coalitionary proactive aggression. Whether a group or tribe adpots such behavior depends entirely on the experiences and dominant norms, mores, and values of the group. Groups with excessively exclusionary values adopt such behavior both to prove and protect their falsely adopted "special" status.
It's really simple- murder everyone who doesn't think or act like you and you have more resources for those more like you. Then you have to be nice to everyone who is left, unless they deviate from the social norm. Then you need to get rid of them.
I am not sure but it seems to me that at least in most major Western cultures only the remnants of tribal culture remain, the positions of power and authority are now business related, and for the most part these relationships are outside the family considered as a tribe. Position and to an extent personal success in such cultures is not guaranteed.
There are other cultures which are more strictly tribal, where social positions are given in birth, where a lowly individual may have very little chance of moving beyond the position of their birth. Life is easier on tribal members in the sense that they don't have struggle to find their way in life, certain possibilities have been predetermined for them from birth