Evolutionary psychiatry and the schizophrenia paradox: a critique

Evolutionary psychiatrists invariably consider schizophrenia to be a paradox: how come natural selection has not yet eliminated the infamous ‘genes for schizophrenia’ if the disorder simply crushes the reproductive success of its carriers, if it has been around for thousands of years already, and if it has a uniform prevalence throughout the world? Usually, the answer is that the schizophrenic genotype is subject to some kind of balancing selection: the benefits it confers would then outbalance the obvious damage it does. In this paper, however, I will show that the assumptions underlying such evolutionary accounts of schizophrenia are at least implausible, and sometimes even erroneous. First of all, I will examine some factual assumptions, in particular about schizophrenia’s impact on reproductive success, its genetics, its history, and its epidemiology. Secondly, I will take a critical look at a major philosophical assumption in evolutionary psychiatric explanations of schizophrenia. Indeed, evolutionary psychiatrists take it for granted that schizophrenia is a natural kind, i.e. a bounded and objectively real entity with discrete biological causes. My refutation of this natural kind view suggests that schizophrenia is in fact a reified umbrella concept, covering a heterogeneous group of disorders. Therefore, schizophrenia, as we now know it, simply doesn’t have an evolutionary history.status: publishe