Apes don’t get schizophrenia. Apes also don’t have culture.
Why are studies where twin babies are separated at birth needed in heritability studies of schizophrenia? Geneticists can’t nail down the genes. Given twin babies separated at birth have similar incidences of schizophrenia then various environmental influences are supposedly ruled out. The take away point is that heritability studies in schizophrenia are not finding genes that confer heritability rather the evidence for environmental effects is ruled out by twin studies where babies are separated at birth so schizophrenia susceptibility must be largely genetic.. The case for the genetic basis of schizophrenia is entirely circumstantial.
Independent assortment occurs where alleles of two different genes get sorted into gametes independently of one another. In research on the genetics of schizophrenia 108 independent genetic loci have been found to be associated with schizophrenia. Apparently these 108 genetic loci are not being inherited together. So what does the genetic theory of schizophrenia amount to – ‘Bad stuff happens. mysteriously’.
There is a lot of speculation on why only humans can get schizophrenia..Some have 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. I would not say the quality is a yet unknown quality though I would strongly agree that the quality is uniquely human The quality is culture.
;Schizophrenia is epigenetic in origin. So are various persistences in culture. Education can, of course, matter too. The case for the genetic basis of schizophrenia is, I think, unfounded. Differences in genetic makeups can not explain various persistences in culture. . However cultures are persistent.
Employing the method of Sherlock Holmes slightly modified, ‘When you have eliminated all that is unfounded then whatever remains, must be the truth.’ Heritability of schizophrenia is due to transgenerational epigenetic inheritance. Various persistences in human cultures are also due transgenerational epigenetic inheritance. Scientists in terms of transgenerational epigenetic inheritance in humans now hold that ‘transgenerational epigenetic inheritance of humans does not exist because we have not found it’ which is not a scientific way of proceeding.