# Schizophrenia and the Evolutionary Perspective - URL: https://alisanburak.com/en/sizofreni-ve-evrimsel-bakis - Language: en - Last updated: 2026-09-15 - Page title: Schizophrenia and the Evolutionary Perspective | Assoc. Prof. Dr. Alişan Burak Yaşar > Why does schizophrenia occur at similar rates across all societies? An attempt to explain it through evolutionary psychiatry and the concept of the “social This page was translated automatically from Turkish. [Read the original](https://alisanburak.com/sizofreni-ve-evrimsel-bakis) [← Back to blog](https://alisanburak.com/en/blog) # Schizophrenia and the Evolutionary Perspective October 5, 2020Articles in Bilim ve Ütopya [Görsel: Schizophrenia and the Evolutionary Perspective] Like evolutionary biology, evolutionary psychiatry asks questions to obtain answers that can advance psychiatry: “How did our species adapt?”, “What are the evolutionary costs of becoming human?”, “Why does the mind not become better adapted despite various adverse conditions?” To answer these questions, evolutionary psychiatry focuses on the beginning of the process—that is, on humans in ancient times. Millions of years ago, as the climate and environmental conditions changed, our hominin ancestors began to live on Africa’s vast grasslands. Over 3 million years, our brain volume tripled. Our ability to use fire and tools developed. Living in communities led to the development of our language skills. Speech made our social lives even more complex. We began to build culture. Over time, our cultural evolution surpassed our biological evolution in both speed and acceleration. Yet, from the outset, the human mind, like the body, developed under these savanna conditions and evolved to adapt to them. Some of today’s mental health problems are thought to be associated with the structural evolution of our brains lagging far behind the demands of the modern world. For example, the more primitive parts of our brain, known as the brainstem and limbic system, are still equipped with the alarm systems of our wilderness survival mode. Even today, these alarms operate as they did to keep humans alive under the dangerous conditions of the savanna, when life expectancy was much shorter than it is now, even at the cost of more adverse consequences in the long term. Meanwhile, the prefrontal cortex, the distinctly human part of our brain, enables us to think and to reflect on our own thinking. This region, which reasons about other people’s minds through what we call “theory of mind” and makes rational decisions, can carry out longer-term analyses and make plans accordingly. Nevertheless, the alarm system of our primitive brain sometimes gives a false alarm in keeping with the system of ancient times and remains stuck in that alarm state, as in post-traumatic stress disorder… The conditions of those early times therefore played a crucial role in determining which mental adaptations would be favored during natural selection in our species, and studying these adaptations today guides us in understanding and making sense of many disorders. This guidance can be particularly useful for making new scientific discoveries or interpreting existing knowledge. An evolutionary perspective helps us at this point. Here, it may be useful to briefly consider what philosophers of science have to say. Philosophers of science have described a “cabling” methodology in which multiple strands of evidence are interwoven to establish a robust evidential foundation. Unlike arguments that form a logical “chain” of sequential links, the cabling method values the inclusion of incomplete evidence. Some cognitive psychologists argue that the cabling method is scientifically powerful because it is both robust—a parallel strand can compensate for a gap in another—and constrains wild hypotheses that would take the researcher too far afield. Thus, an evolutionary perspective, which is open to speculation and draws on it, can be regarded in this context as a field with both strengths and weaknesses. Humans live in groups. In human evolutionary selection, being alert to both external threats and threats within the group, and being able to act when necessary even in response to a false alarm, play an important role. In accounts of our species’ survival in the struggle thought to have taken place between Neanderthals and our species, various views suggest that the ability to be more defensive or suspicious contributed to survival. In this article, we will attempt to discuss the possible evolutionary advantages of schizophrenia and related conditions (the spectrum) for our species and the group, if not for the individual. One reason for this is that even schizophrenia at the syndromal level occurs at similar rates across cultures and societies. If this disorder persists at a stable rate across all societies, regardless of the passage of time, what might this mean? What evolutionary purpose might the persistence of this disorder serve, or which of our characteristics might account for it? Could the “traces” that are also common in people without the disorder, although they do not meet all its criteria, benefit our species? Might schizophrenic traits sometimes be useful when they remain below a certain threshold, with illness emerging only when that threshold is crossed? Or is schizophrenia a by-product—a side effect—of the development of the “human-like thought” system that distinguishes our species so markedly from others in developmental terms? Modern humans have brains that are highly attuned and adapted to complex interpersonal relationships. This “social brain” is an important part of our minds. Papers that view schizophrenia as a disorder of brain evolution also describe it as a social disorder. There is anatomical, functional, and clinical evidence for this. Accordingly, some papers regard schizophrenia as a “phenomenon of social alienation.” Before turning to this, let us briefly examine the diagnostic system that contemporary psychiatry has, of necessity, developed through statistical data and experiments. What is schizophrenia? Schizophrenia is a psychiatric disorder characterized by hallucinations, delusions, and disturbances in the structure\process of thought that affect a person’s daily life. These hallucinations may be visual, but they can also consist solely of hearing sounds, experiencing sensations of touch, and so on. A delusion is defined as a fixed belief that cannot be changed despite clear evidence that it is untrue. In schizophrenia, these beliefs are sometimes bizarre (far removed from reality). Two important features of the disorder are a distinctive withdrawal and changes in perception and interpretation. In schizophrenia, we broadly refer to hallucinations, delusions, and disturbances in the perception of reality as “psychosis.” These are elements of the syndromal definition of schizophrenia. However, psychotic experiences can occur outside schizophrenia. Not every psychotic experience means schizophrenia. For example, psychotic symptoms can also occur in severe depression, during substance use, or in the presence of a brain tumor. All instances of psychosis are described as psychotic experiences, whether or not they lead someone to seek help, whether or not they are part of a psychiatric condition, and whether they occur once or persist over a long period. When they become part of an illness, they are called symptoms. In some disorders, psychosis is essential and required for the diagnosis; in others, it may be an additional symptom of another syndrome. Psychotic experiences are much more common in the population than is generally assumed. Any individual’s lifetime probability of experiencing psychosis is as high as approximately 4 percent. This can be considered an important indication of how sensitive our minds are to psychotic symptoms and how predisposed to psychosis their default settings may be in response to even the slightest “change.” In this regard, the tendency toward paranoid thinking (delusions) in schizophrenia is thought to persist as a feature outside the brain regions associated with conscious awareness. Humans, who evolved under group selection pressures, would naturally be expected to have readily available, rapidly functioning systems concerning other people. To draw an analogy with a medical condition, in sickle cell anemia, a mutation that causes anemia means that people live with greater pallor and fatigue. However, when people who contract certain types of malaria are examined, those with sickle cell anemia are known not to be affected by these types of malaria and to have immunity against them. They would be the survivors of a malaria outbreak. A similar context can be considered for paranoia. In an environment where groups of humans lived together under threat from nonhuman predators or in conflict with other humans, a somewhat higher prevalence of these traits or tendencies may have provided an advantage for the survival of the species at certain critical times. Science has not yet definitively established which aspects of the mind are affected in schizophrenia and psychotic disorders, or the precise nature of the associated dysfunction. Nevertheless, research and investigation now allow us to call the following combination of symptoms schizophrenia “as a syndrome.” Of course, as noted above, although schizophrenia—which is commonly equated with psychosis—includes psychotic symptoms, psychotic symptoms that do not meet the following conditions are not defined as schizophrenia. 1. At least one of the following symptoms must be present: hallucinations, delusions, or disorganized speech. In addition to these, disorganized behavior and reduced emotional and motivational engagement are considered, and at least two of these five symptoms must be present overall. ## 2. The symptoms must impair quality of life. 3. They must last at least 6 months. (This duration is not required if treatment is received immediately.) Although they involve many other nuances and details, these are, broadly speaking, our diagnostic criteria for schizophrenia in simplified form. Only a psychiatrist assessing these criteria through a detailed interview can make the diagnosis. These criteria emerge from years of following patients with similar symptoms who improve with similar treatments, and from research documenting these findings. Such research is essential for identifying disorders and planning treatment. These studies have revealed an interesting result. Various disorders associated with genetic and environmental factors are more or less common in particular communities and settings. For example, the anemia disorder called familial Mediterranean fever (FMF) is common in populations of the Mediterranean region. Yet, despite being defined as a syndrome, schizophrenia occurs at almost the same frequency worldwide, at approximately 4 to 9 per thousand. Although a genetic characteristic associated with FMF explains its distribution, no genetic characteristic clear enough to explain this pattern in schizophrenia has yet been identified. If schizophrenia represents the pathological end of the range of symptoms seen in schizophrenia and psychotic disorders, other descriptions that may also occasionally include psychotic experiences can be found at the nonpathological end of these symptoms. For example, the criteria for schizotypal disorder are as follows: Interpersonal difficulties characterized by acute discomfort with close relationships and a reduced capacity to form them, together with cognitive or perceptual distortions and eccentric behavior. In addition, five of the following must be present: Ideas of reference; magical beliefs, such as clairvoyance or a sixth sense, that are inconsistent with cultural and societal norms; unusual perceptual experiences and bodily sensations; markedly odd thinking and speech; suspiciousness; restricted emotional expression; markedly unusual behavior and appearance; a lack of close confidants; and persistent social anxiety involving suspiciousness. The schizotypal condition, defined by the presence of five of these symptoms, does not indicate schizophrenia, and the presence of only four means that the schizotypal condition is not present either. Thus, although each of these criteria and definitions appears important in terms of psychotic traits, we cannot claim that they always constitute an illness. The fact that schizophrenia is not a “natural category,” and that its specific biological causes cannot be clearly established, presents an important phenomenological problem. Despite nearly 10 years of mapping the human genome, the genes responsible for schizophrenia have still not been found. For these reasons, schizophrenia remains an ambiguous, difficult-to-distinguish, and mysterious phenomenon for clinicians today. This creates difficulties when discussing its evolutionary history. If the brain region or genetic basis responsible for schizophrenia were clearly established, there would be greater scope for a more robust discussion of its evolutionary nature and adaptive\maladaptive characteristics. Nevertheless, its similar prevalence across societies, whatever its biological basis, may provide important information in an evolutionary context, and this perspective may shed light on biological research. Beyond the biological background, “culture” and “cultural evolution” may be precisely the areas of investigation we need here. This is because schizophrenia is considered a heterogeneous syndrome encompassing many subconditions. Nevertheless, with today’s psychiatric science, the great majority of people with schizophrenia are treated effectively with medication and psychotherapy. Since the term schizophrenia first emerged, we have used it to describe a fundamental split between internal thought and understanding, on the one hand, and integration with the world or emotional connection, on the other. At this point, Minkowski, a student of Bluer, one of the most important figures in the study of schizophrenia, offered an important new perspective. Minkowski regarded schizophrenia as a disconnection between reason and intuition, describing the former in terms of analysis and abstract thought and the latter in terms of the vitality and temporal dynamism of experience. Both Bluer and his student defined the central problem of schizophrenia as the disconnection and alienation a person feels from their social self and the social world. Social adaptation is a crucial prerequisite for learning the knowledge and skills essential to survival. Moving along the phylogenetic line from our relatives toward humans, the complexity of social functioning has gradually increased. For example, unlike our more distant relatives, monkeys make extensive use of cooperation and alliances and display long-term friendships. They devote time to social grooming and reconciliation. They even use techniques of social manipulation. “Theory of mind” and representational intelligence, described following an experiment with chimpanzees in 1978, are also evident in monkeys. Theory of mind has been defined as the ability to explain other people’s observable behavior mentally through corresponding changes in one’s own mind—the capacity to mentalize. Many authors argue that nonhuman apes such as chimpanzees and orangutans possess basic theory-of-mind skills and that the origins of this capacity for social cognition date back approximately 10 million years. Contrary to popular belief, increasing brain size is not solely responsible for the development of modern human cognition and theory of mind. Indeed, the neural connections linking different brain regions are far more important here. Some researchers suggest that the evolution of social behavior is associated with the reorganization of the brain rather than its growth. For example, moving phylogenetically toward humans, connections involving the right parietal cortex—a region on the right side of the brain among those involved in social behavior and social cognition—have been shown to develop and become markedly stronger. Research into the development of social and language skills in infants has shown that social awareness and interpersonal development are necessary before “individual consciousness” and a sense of “self” emerge. The assertion by the founders of social psychology that “meanings emerge through social interaction” is very important. Some authors argue that mothers “teach through shared experiences with their babies” through imitation games and that “the infant’s belief in a shared world of subjectivity arises from a sequence of physical interactions.” In this context, individual consciousness can be said to be produced from collective meanings—from “culture.” Infants learn the meaning of language through their experiences of the social world in which they are immersed. Unlike other living beings, humans are organisms whose brains continue to develop after birth. Structural changes also occur during this period. The increase in brain connections and the pruning of some connections proceed very rapidly during the first 2 years after birth and continue throughout life, albeit at a slower pace. The most basic cellular changes occur through the addition of a methyl group to a molecule—that is, through methylation. A gene is often activated or silenced through a single methylation event. Considering that methylation is thought to occur most extensively in the brain, and that cell pruning and proliferation in the brain proceed very rapidly in the first few years after birth, it is clear how sensitive our brains are in early life, both to harm and to the conditions necessary for healthy development. Interestingly, schizophrenia often emerges before the age of 25. Impairments in theory-of-mind ability can be detected both in schizophrenia and in relatives of people with schizophrenia. In this context, examining it as a social syndrome appears particularly important for defining schizophrenia. Thus, in human biological and culturally appropriate development, the development of the brain and its connections is likewise vulnerable to threats and to being diverted onto a different path. Mirror neurons can be broadly described in terms of two people developing simultaneous, synchronized activation during communication. Mirror neurons play a critical role in empathy and related abilities. The identification of mirror neurons in the prefrontal cortex, a region at the front of the brain, in both macaques and humans has provided important findings about the neural foundations of social cognition, mental-state attribution, and empathy. One person’s action is represented in another person’s mind. Indeed, beyond the action itself, the intention inferred from a macaque’s behavior produces changes resembling behavioral activation in the brain of another macaque. One symptom of schizophrenia is the distorted judgment that another person is making harmful plans concerning them (ideas of reference, etc.). This can be considered a feature of our social brain. The social brain is defined as the cognitive and emotional systems underlying the abilities that form the basis of social cognition, social behavior, and emotional sensitivity. Scientists associate social perception with face perception, theory of mind, and short-term memory. In schizophrenia, theory of mind concerning other people’s mental states is impaired, and distorted cognitions arise. Recognition of emotion from facial expressions is also impaired in schizophrenia. Returning to the question of why dysfunction in this critical system persists… Schizophrenia is thought to have emerged around 60,000 years ago. As with many psychiatric disorders, “balancing selection” is a focus of evolutionary accounts of schizophrenia. Most of those who have ventured to understand schizophrenia from an evolutionary perspective have arrived at a model of balanced polymorphism, arguing that hidden advantages associated with the genotype serve to offset the evolutionary disadvantages associated with the disorder. This model, which is difficult to test scientifically, suggests that the absence of a reproductive disadvantage among first-degree relatives of people with schizophrenia (who are genetically close to them) is consistent with the fundamental principles of Darwinism. Nevertheless, one criticism of this view is the following: even if it has an adaptive effect, why does this multifactorial genetic basis continue to be inherited when it causes serious harm beyond a certain threshold? Another interesting point is that the content of delusions is similar across cultures. This also points to a feature associated with evolution and being human. There are similarities in the content of paranoia in psychotic states. For example, men more often have delusions of being harmed by unfamiliar men, whereas women more often have delusions of being harmed by people within their own personal circles. The significance of this pattern becomes somewhat clearer when we consider the living conditions of human groups in prehistoric times. Given that the risk of schizophrenia is 10% among relatives of individuals with schizophrenia and 50% among identical twins, it is clear that genetic transmission is involved, whatever its mechanism. This is described as the “schizophrenia paradox.” Why does schizophrenia continue to occur at such a stable rate? Although it creates some reproductive disadvantage and involves a somewhat reduced life expectancy for various reasons, it is indeed striking that schizophrenia occurs in all societies at a stable and high rate of approximately 1%. Returning to the view that genes predisposing to schizophrenia, and their ongoing activation and silencing processes, have been favored by positive selection and confer a survival-related advantage on carriers who do not manifest the disorder but retain its underlying predisposition, some advantage is thought to exist for people who do not display symptoms of schizophrenia or occupy a high-risk borderline psychotic state, and in whom the partial expression of these genes does not exceed a certain threshold. This advantage may involve the ability to think outside cultural and societal norms and may be related to creativity. Another important hypothesis is that schizophrenia is a by-product of evolutionary development. This alternative hypothesis suggests that it may have emerged as a directly disadvantageous by-product of the mental and cultural characteristics that arose during the evolution of the human brain. This view, which regards schizophrenia as a by-product or costly consequence of social evolution, likewise emphasizes its presence and persistence in our species. According to this view, the genetic predisposition to schizophrenia exists because of the “normal genes” responsible for neurodevelopment. Through reciprocal gene–environment interactions, an adverse social environment may trigger susceptible genes, allowing a genetic predisposition to manifest as an illness. Returning to the first of these two views, balancing selection, the basic idea is that there is a threshold beyond which a previously adaptive variation becomes maladaptive. The process whereby the prevalence of these survival-enhancing variations increases under selection up to a threshold, beyond which fitness falls sharply, has been termed cliff-edge fitness. Let us ask: “Even if this gene has an adaptive effect, why does it continue to be inherited when it causes serious harm beyond a certain threshold?” One answer may be antagonistic pleiotropy. In Mendelian inheritance, an antagonistic pleiotropic effect means that the two corresponding codes in the DNA helix, called “alleles,” simultaneously carry advantageous and disadvantageous characteristics in equal measure, preventing the disadvantageous characteristic from being eliminated. Returning to the second view, it rests particularly on the following observations. It is clear that many of our mental abilities are acquired through a prolonged period of maturation. Unlike those of other living beings, the human brain continues to develop after birth, is influenced by culture and society during that development, and is able to develop in this way because of our genetic makeup. In other words, the genes that make us human may be the same genes that make us people with psychiatric disorders. Our capacity for theory of mind and our ability to engage in socially appropriate interactions may come together with the capacity to develop dysfunctional brain connections and a disorder such as schizophrenia. This process, which probably accompanied the development of our capacity for “language,” is thought to be associated with relevant macromutations or a group of small mutations. Marked impairments in schizophrenia also involve “language.” Here, language has a broader meaning in the context of our distinctly human capacity for thought. Having discussed culture and language so extensively, we should finally touch briefly on the formation of group norms and the influence of culture on perception. How perception is influenced by a group has been well known since the work of Muzaffer Şerif. In a group, the views expressed by those before you about a given reality affect your perceptual processes even before your consciously thinking mind, even if those views are diametrically opposed to reality. Perception precedes consciousness. What earlier speakers, the group, or the leader say influences the establishment of the “norm.” In schizophrenia and related disorders, thoughts and statements that deviate from group norms may also play a critical role in cultural development and human existence by helping to balance norms in ways that maximize the group’s survival and preservation. In conclusion, if we consider human consciousness and experience to exist together with the social environment and culture, turning toward a social model of schizophrenia and the “phenomenon of social alienation,” rather than an individual model, may be useful for new research. Of course, all such evolutionary assessment requires greater recognition of schizophrenia as a “natural diagnostic category” and a better understanding of it and its subgroups. ## Further Reading Suggestions ## References - Yildirim EA, Yıldızhan E, Öztürk N. Şizofreni; Evrime Ödenen Bir Bedel Mi? (2016) Toplum ve Hekim, 31,5 2-400 - Bora, E. (2009). Şizofreni Spektrum Bozukluklarında Zihin Kuramı. Turk Psikiyatri Dergisi, 20(3). - Aytaç, Ö., & Kurtdaş, M. Ç. (2015). Sağlık-Hastalığın Toplumsal Kökenleri Ve Sağlık Sosyolojisi. Fırat Üniversitesi Sosyal Bilimler Dergisi, 25(1), 231-250. - Taycan, O. (2017). - Adriaens, P. R., & De Block, A. (Eds.). (2011). Maladapting minds: Philosophy, psychiatry, and evolutionary theory. Oxford University Press. - Brüne, M., & Brüne-Cohrs, U. (2006). Theory of mind—evolution, ontogeny, brain mechanisms and psychopathology. Neuroscience & Biobehavioral Reviews, 30(4), 437-455. - Brüne, M., Ribbert, H., & Schiefenhövel, W. (2003). The social brain: Evolution and pathology. John Wiley & Sons Inc. - Brüne, M., Belsky, J., Fabrega, H., Feierman, H. R., Gilbert, P., Glantz, K.,... & Troisi, A. (2012). The crisis of psychiatry–insights and prospects from evolutionary theory. World Psychiatry, 11(1), 55. - American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (DSM-5®). American Psychiatric Pub. - Şizofreni ve Diğer Psikotik Bozukluklar (2018) Türkiye Psikiyatri Derneği - Yasar, AB. (2018) - Srinivasan, S., Bettella, F., Hassani, S., Wang, Y., Witoelar, A., Schork, A. J.,... & Dale, A. M. (2017). Probing the association between early evolutionary markers and schizophrenia. PloS one, 12(1), e0169227. --- *This article was first published in the Evolutionary Psychiatry special feature of Bilim ve Ütopya magazine (2020).* [← Previous Book Recommendations](https://alisanburak.com/en/kitap-onerileri)[Next → Biology, Antidepressants, and Psychotherapy](https://alisanburak.com/en/biyoloji-antidepresanlar-ve-psikoterapi) --- Kaynak / Source: https://alisanburak.com/en/sizofreni-ve-evrimsel-bakis İletişim / Contact: Bağdat Caddesi, Veli Güneysu Apt. No:453 K:4 D:9, Suadiye / Kadıköy, İstanbul · +90 532 642 95 25 · info@alisanburak.com · https://alisanburak.com/bagdat-caddesi-psikoterapi-iletisim