Researchers studying Nazca boobies of the Galápagos Islands found high correlations between degree of aggressive behavior among adults and the amount of abuse they endured as nestlings. The findings have implications for those who study human psychology and behavior, as some social scientists argue that abused children are statistically more likely to become abusers later in life.
Anderson has previously observed adult Nazca boobies biting and pecking little chicks while the parents were foraging for food. He argues that the aggressive behavior is initially kicked into overdrive when the insurance offspring (described in Evolution Battles – Parent and Offspring Rivalry) is killed by its sibling.
Drawing upon understanding of a common physiological and psychological interaction, Anderson believes that a high dose of testosterone is required to surge through the young chick in order for it to act in such a violent way. After killing its sibling, the young birds are abused by older ones in the colony, and the cruel cycle simply continues.
The findings have interesting consequences on important correlations of violence in humans. Though studies on non-human primates in captivity have demonstrated that early abuse leads to a greater likelihood of developing violent relationships among both peers as adults, Anderson states his “study is the only time we’ve observed a cycle of violence in a natural state.”
Anderson hopes to design future studies that evaluate the aggression of abused chicks and relate those findings to abusive human behavior.