Anne Campbell was Professor Emerita in Psychology at Durham University. She gained her doctorate in experimental psychology from Oxford University in 1977. Her principal research focus was the evolutionary psychology of women’s aggression, with a particular emphasis on the role of fear in restraining aggressive behaviour. Catharine P. Cross is a Lecturer in Psychology at the University of St Andrews, UK. She gained her PhD from Durham University in 2011 and her current work focuses on sex differences in human social behaviour and the contextual factors that modify these. Lee T. Copping is a Lecturer in Psychology at Teesside University, UK. He gained his PhD from Durham University in 2015 and his current work focuses on sex differences in human behaviour and the measurement and application of life history theory.