The term ‘schizophrenia’ refers to a group of disorders that seem to occur worldwide, with clinical pictures being strikingly similar across cultures. Evolutionary explanations of these disorders are warranted for at least two reasons: the first concerns their prevalence in all known ethnicities; the second relates to the need to explain the paradox as to why the conditions are maintained despite the greatly decreased fecundity of the affected individuals. Accordingly, a plethora of heterogeneous hypotheses – unparalleled among other psychiatric disorders – have been put forth, some of which deal with genetic considerations, others with environmental risk factors, and a few consider the adaptive advantages associated with the genes that predispose to schizophrenia. None of the evolutionary scenarios has the potential to account for the diversity of the symptomatology or to cover all of the biological and non-biological aspects of schizophrenia or schizophrenia spectrum disorders. This chapter aims at discussing the most relevant evolutionary hypotheses of schizophrenia, arguing that a symptom-based approach to psychotic disorders from an evolutionary perspective may improve upon the existing models of schizophrenia.