Background: Hierarchical and territorial behaviour are widespread in animals and humans. The consequences of defeat have been linked to depression in humans. However, hierarchical and territorial behaviours are not mentioned in ICD10 or DSM1V. I therefore investigated the coverage in relevant textbooks. Method: I searched the indices of books on Animal Behaviour, General Psychology and General Psychiatry for entries on Hierarchy, Territory and Dominance. Results: A paradox is revealed. Hierarchical and territorial behaviour are widespread in both animals and humans but are neglected in textbooks of human behaviour and mental problems. Four hypotheses are put forward to explain this paradox and explore its implications.Three testable predictions follow from these hypotheses.Case examples are given to illustrate the existence of, and the consequences of defeat on, internal hierarchies. Limitations: These hypotheses and predictions are theoretical and require confirmation or refutation by neuroimaging and prospective studies. Conclusions: A neglect of human hierarchical behaviour by clinicians is suggested and discussed. The concept of internal hierarchies, if confirmed, may throw light on human striving, the emotions of defeat and the therapy of depression.