Human collective aggression: A behavioral ecology perspective

Abstract

Moller (1967/68) proposes that the presence of a large number of adolescents and young adults in a population is a precursor of violent conflicts. But acts of collective aggression are typically perpetrated by males, particularly young males between 15 and 30 years of age. This marked sex difference in the degree of participation is found in all human societies, and it has persisted since the beginning of recorded history. Sexually dimorphic behaviors are invariably found in the context of reproduction, and we discuss male coalitional aggression as a reproductive fitness-enhancing social behavior. This type of social behavior may not increase the welfare of an entire population but it is likely to promote the fitness of the coalition participants. This study argues that the age composition of the male population should be regarded as the critical ecological/demographic factor affecting a population's tendency toward peace or violent conflicts. Our analyses of interstate and intrastate episodes of collective aggression since the 1960s indicate the existence of a consistent correlation between the ratio of males 15 to 29 years of age per 100 males 30 years of age and older, and the level of coalitional aggression as measured by the number of reported conflict related deaths.