How does social isolation during development affect aggression in animals?

Social isolation during development is a significant environmental factor that influences adult behavior in many species. Research indicates that individuals reared in social isolation are particularly prone to increased levels of aggression as adults.1

This outcome highlights that aggressive behavior is not solely the result of instinct or genetics but emerges from a complex, continuous interaction between an animal's inherited genes and its pre- and postnatal environment. While genetic factors—such as those on the Y chromosome in mice—can predispose an animal to aggression, environmental experiences during development, including social isolation, play a profound role in shaping whether and how an animal fights later in life.1

Other developmental environmental factors that can increase adult aggression include food deprivation and rough handling by mothers. Ultimately, these influences demonstrate that an animal's adult behavior is shaped by the specific conditions in which its genes are expressed.1