Chapter 11: Aggression

Aggression from Sociobiology: The New Synthesis provides a comprehensive analysis of the biological, evolutionary, and physiological dimensions of aggression, defining it as a behavior that abridges the rights of others to ultimately influence genetic fitness. The text systematically categorizes aggression into eight distinct functional forms, including territorial defense, dominance assertions, sexual aggression, parental disciplinary actions, weaning conflict, moralistic enforcement, predatory attacks, and antipredatory maneuvers. Aggression is framed as a key mechanism of intraspecific and interspecific competition, particularly when density-dependent factors like food and shelter become limiting resources, though it is noted that some species utilize non-aggressive "scrambling" techniques instead. The chapter challenges earlier ethological assumptions by presenting evidence of lethal violence and cannibalism in vertebrates such as lions, hyenas, and primates, refuting the notion that animals rarely kill conspecifics. It further explores indirect competitive strategies, such as mutual repulsion through chemical signaling and pheromones in insects and rodents. The evolutionary limits of hostility are examined through the concept of inclusive fitness, where the costs of injuring relatives or neglecting other survival tasks ("aggressive neglect") balance against the benefits of dominance. Proximate causes of aggression are detailed, including external triggers like xenophobia toward strangers, the distribution of food resources, seasonal breeding cycles, and the exponential increase in conflict associated with crowding. Physiologically, the summary explains the endocrine control of aggression, highlighting the role of androgens (testosterone) in maintaining preparedness, the immediate "fight or flight" response mediated by epinephrine and norepinephrine, and the long-term stress responses governed by adrenal corticoids as described in the General Adaptation Syndrome (alarm, resistance, and exhaustion stages). The chapter concludes by discussing human aggression not as a neurosis or innate "blood lust," but as a genetically programmed, adaptive potentiality that emerges under specific environmental stresses and social pathologies.