Donald G. Dutton said this quote

“ What are the final lessons learned? I came to the conclusion that the most powerful human motive by far is the striving for attachment to loved ones in perpetuity. Humans will do anything for this, including blowing themselves (and others) to pieces. I learned that tribalism is universal. It may start with the attachment to another (typically, the mother and disinterest in those who are not her), and it may be furthered by the division of in-group as those we recognize and out-group as the rest, but our capacity for symbolism established in- and outgroups in us all, and we view their actions completely differently. We need, if we are to survive, a sense both of humanity as a tribe and of humanity’s potential for radical violence. If we delude ourselves that we are the civilized entity we appear to be on the surface, we are doomed to repeat the mistakes of the past, only with more powerful and devastating weapons. ”