Back in the 80’s, there was the McNeil-Lehr Newsreport, on public television. One night, in a ten minute segment, they introduced a group of anthropologists working in the Amazon region of Brazil. They had been studying one tribe, making contact, and learning about them.
After some months or longer, they came across another tribe in the same region. It seemed a good idea to introduce them to each other.
Not all ideas work out. Upon getting both tribes together, their immediate reaction was to try to murder each other.
While that was avoided, the trait has held on tenaciously throughout history and so far seems eternal. Alas.