Culture is one factor that plays a role in aggression. Tribal or band societies existing before or outside of modern states have sometimes been depicted as peaceful 'noble savages'. The ǃKung people were described as 'The Harmless People' in a popular work by Elizabeth Marshall Thomas in 1958, while Lawrence Keeley's 1996 War Before Civilization suggested that regular warfare without modern technology was conducted by most groups throughout human history, including most Native American tribes. Studies of hunter-gatherers show a range of different societies. In general, aggression, conflict and violence sometimes occur, but direct confrontation is generally avoided and conflict is socially managed by a variety of verbal and non-verbal methods. Different rates of aggression or violence, currently or in the past, within or between groups, have been linked to the structuring of societies and environmental conditions influencing factors such as resource or property acquisition, land and subsistence techniques, and population change.