From the classic anthropology text Patterns of Culture by Ruth Benedict
Warfare is not the expression of the instinct of pugnacity. Man's pugnacity is so small a hint in the human equipment that it may not be given any expression in inter-tribal relations. When it is institutionalized, the form it takes follows other grooves of thought than those implied in the original impulse. Pugnacity is no more than the touch to the ball of custom, a touch also that may be withheld.