The early Spring (March-April, 2019) issue of “Foreign Affairs” has a major piece on tribalism by Nicholas Sapolsky, “Your Brain on Nationalism: The Biology of Us and Them”.
The picture shows a chimpanzee at the Singapore Zoo. Indeed, chimpanzees (not bonobos) are fiercely tribal and their social organizations are geared for conflict with rival groups.
His article stresses that humans, with even larger brains, are able to belong to more that one group at the same time. Besides setting the stage for intersectionality, it creates new opportunities and challenges for cooperation.
Tribalism is relative. There’s a video of a cat encountering an octopus on a pier. My own inclination was to “bond” mentally with the cat, who is more like me than an invertebrate octopus (whose intelligence is actually comparable). Race, based on the most superficial of characteristics that first develop when populations are isolated from one another, still generate tribal feelings of us and them. Many people, myself included, could not imagine sexual desire for someone of a different race.
But nationalism is more than just ordinary tribalism, it is aggregate tribalism, that set up the modern state system.