John has an extensive career researching and teaching psychology. Notably, this is in the area of aggression, sex and gender, and grief and loss, informed by evolutionary principles. He has many publications in a wide range of journals, including Biological Reviews, Psychological Bulletin, Behavioural and Brain Sciences, and Animal Behaviour. He received the Scott Award in 2016, from the International Society for Research on Aggression, for his lifetime’s achievement in this research area.