Is there an evolutionary advantage of schizophrenia?

Schizophrenia is a universal disorder with strongly genetic aetiology. A constant prevalence rate, universally, in the face of reduced fecundity leads to the argument here that an evolutionary advantage exists, but not solely for schizophrenia. Possible areas of advantage are examined and it is argued that schizophrenia exists as a costly trade-off, in the evolution of Homo sapiens, as a by-product of a yet unknown uniquely human quality. The reason it has stayed in existence is due to a combination of advantages bestowed upon the kin, the group and, to a lesser extent, individuals who suffer from the disorder; these all contribute a different type of advantage, each of which alone would not be sufficient. Further, the evidence for the other advantages alone lack the rigour of evidence seen in the by-product theories, which provide as yet unparalleled comprehensive evolutionary evidence.