A data base developed from the Memorial Institute for the Prevention of Terrorism’s (MIPT) Terrorism Knowledge Base for the years 1998–2005 was provided to participants in the workshop. The distribution of fatalities in terrorist attacks is, like many outcomes of human social and economic processes, heavily right-skewed. We propose an agent based model to analyse this, and to enable generalisations to be made from the historical data set. The model is inspired by modelling developments in cultural evolutionary theory. We argue that a more appropriate ‘null’ model of behaviour in the social sciences is on based upon the principle of copying, rather than the economic assumption of rationality in the standard social science model.