In my opinion, the result of our tribalism tendency that we are currently discussing has very little to do with “instinct”, and it is rather the result of generational social conditioning we are exposed to since the day we are born; values and biases adopted unquestioningly from our caretakers, educators, and the culture and political reality that we grew up and associate with.
If a child without preexisting established knowledge or exposure can naturally make friendly associations toward an abstract-looking plushie that has one big eye and 10 legs, which has nothing similar to the appearance of a human, then the reason they would fear or hate people of different skin color or cultures is apparent.