The prevalence of schizophrenia among humans is estimated at 0.4-1% of the adult population. This disease doesn’t appear to occur in non-human species, yet other mental health symptoms such as depression and anxiety have been observed and analyzed among animals. This discrepancy poses the question as to why schizophrenia still exists and has not been phased out through natural selection. Since the foundation of schizophrenia is highly genetic in nature, studies have examined how this disease developed exclusively through the evolvement of the human brain. In other words, “psychosis may be an unfortunate cost of having a big brain that is capable of complex cognition.”
Researchers studied specific parts of DNA that appear to be human-specific and affiliated with schizophrenia genes. They found that these variations in human genes are vital to us in specific ways regardless of the potential risks embedded. For example, although these human-specific genes have connections to schizophrenia, they also positively impact the prefrontal cortex, which is an area of the brain responsible for higher-order thought processes. Consequently, impairments in this complex part of the brain are theorized to result in psychosis. In summary, by studying the evolutionary genes closely linked to schizophrenia, researchers could derive more effective treatments and therapies for future cases.
www.scientificamerican.com/article/schizophrenia-may-be-the-price-we-pay-for-a-big-brain/