Desmond Morris, a zoologist, in the book, The Human Zoo (1969), writes: “Man is a tribal animal, and the great super-tribes will always be in competition with one another.” p. 117 of chapter 4: “In-groups and Out-groups.”
Watch below the BBC six-part series “The Human Animal,” presented by Desmond Morris in 1994. Tribalism is covered in the 3rd part.
Nationalism is one form of expression of tribalism. It is the desire to have your nation or tribe be a State. The trouble arises when your tribe or nation is believed to be superior to other tribes or nations. This is what happened in Nazi Germany, especially when the tribe or nation is seen as a Nordic warrior nation, with an exaggerated image of self-importance.