Thanks to twin studies, schizophrenia is one of the few mental illnesses that we know have a genetic inheritance pattern. Schizophrenia often presents as a inability to separate reality from non-reality, where patients often experience hallucinations and stimuli that do not exist, such as hearing voices. Just how this deleterious disease came about to be part of our otherwise social story has been an evolutionary condundrum.
A new, while negative finding, study in Biological Psychiatry may help explain that Neanderthal’s, in particular, can’t be faulted for this mental illness. By doing a GWA of genomes of Neanderthals to modern humans, the researchers found evidence for an association between genetic risk for schizophrenia and markers of human evolution. From that, they looked at regions of the human genome associated with schizophrenia, known as risk loci. They, then, found that these loci were more likely to be found in regions that diverge away from the Neanderthal genome. This means schizophrenia is a modern development, one that emerged after humans diverged from Neanderthals.
We already know that the Neanderthal introgression has brought a higher than average risk of diabetes, and an overall altered immune system. But it seems that that Neanderthals, at least, did not suffer from schizophrenia and that this mental illness is perhaps newer.