Dear listeners, welcome to another episode of the Real Science Podcast. In this episode, we are interviewing Dr. Riadh Abed, a specialist in evolutionary psychiatry. Welcome, Dr. Riadh. We begin the interview by asking you about your work and a brief introduction about yourself.

Firstly, I’d like to thank you for hosting me and for your interest in Evolutionary Psychiatry (EP). I’ll start by introducing myself: I am Riadh Tawfiq Abed, a graduate of the University of Baghdad Medical School in 1974. After completing my residency and military service, I began my training in psychiatry in Baghdad at Ibn Rushd Hospital. Then, in 1979, I travelled to the United Kingdom to complete my specialization. There, I worked in several hospitals during my training, including in Liverpool and Cambridge.

In 1987, I started working as a consultant in psychiatry in South Yorkshire, a county located in the centre of Britain, where I worked for 25 years, including seven years as the medical director of a mental health NHS Trust that provides mental health services to a region with a population of about 0.75 million people spread across three towns/cities. I retired from full time work in the NHS, the British healthcare system, in 2012, and since then, I have been working as a consultant for the UK Ministry of Justice as a member of medical committees, a role I continue to hold to this day.

My interest in Darwinism and its relation to medicine in general, and psychiatry in particular, began in the early 1990s through personal effort and my own readings. Since then, I have published several theories about the Darwinian or evolutionary roots of various mental disorders, including eating disorders, obsessive-compulsive disorder (OCD), and schizophrenia. And, I am now in the process of publishing a theory about the Darwinian roots of personality traits in humans, which will be published in the coming weeks.

In 2016, I managed, in collaboration with some psychiatric colleagues in the UK, to convince the Royal College of Psychiatrists to establish a Special Interest Group (SIG) for evolutionary psychiatry within the college—the first of its kind anywhere in the world. I served as the chair of this SIG for four years, from 2016 to 2020, and I am now in my second and final term as its chair, which began in 2024 and will end in 2028. During the eight years of this SIG’s existence, we have been able to organize six international conferences on Evolutionary Psychiatry, marking the first time this has happened anywhere in the world. Previously, smaller conferences on evolutionary psychiatry had taken place, mostly as part of other general psychiatry or medical conferences. In contrast, we organized six international conferences, inviting speakers from various parts of the Western world, as this topic is not particularly known outside the West.

We uploaded parts of these conferences to YouTube, which is another achievement and another first for EP. Today, we have a YouTube channel with over 65 to 70 lectures from professors and leaders of EP from around the world. Additionally, I co-edited a book which was published by the Royal College of Psychiatrists jointly with Cambridge University, the first time the college has published a book on EP. That’s a brief overview of myself.

What is Evolutionary Psychiatry?

Dr. Riadh, you might have already started addressing the second question I intended to ask, but I’d like to add some details to it. Many listeners may not know the difference between evolutionary psychiatry and evolutionary psychology. Here in the Arab world—speaking for myself and a group of young people involved with Real Science—we had a large meeting about evolutionary psychology, specifically discussing David Buss’s book. So, my first question is: What is evolutionary psychiatry, and what is the difference between it and evolutionary psychology?

Of course, there is a connection between the two. Both evolutionary psychiatry and evolutionary psychology address the function of psychological traits in humans, their Darwinian roots, and how these traits work functionally to aid survival and reproduction. We must remember that evolutionary science studies how traits arising from the Darwinian process help with survival and reproduction—that’s the foundation of all evolutionary science.

Evolutionary psychology looks at how these traits emerged through the Darwinian process of natural selection, while evolutionary psychiatry investigates how disruptions occur in these traits and how we can explain them by understanding the origin of these functional traits. I can expand a bit more on what evolutionary psychiatry is and how it provides us with a deeper understanding of the nature of these disorders.

What piqued my interest most in your research, Doctor, is the many fascinating areas related to the evolutionary perspective on mental illness. However, the first thing that caught my attention was a published study about the prevalence of schizophrenia and its connection to human environmental conditions. It highlights the fact that we currently live under conditions vastly different from our ancestors; in other words human nature was designed for a different set of conditions. Does your research suggest that the modern environment plays a significant role in the incidence of schizophrenia, especially knowing that schizophrenia also has a genetic component? Of course, you’re free to correct my perspective or the way I’ve framed these questions, as I might have misunderstood your intent.

Thank you for the question, but I think it might be best if I first give an overview of what evolutionary psychiatry is, then address the question specifically about schizophrenia. Is that okay? [Omar: Sure.] I’ll start with what evolutionary psychiatry, or Darwinian psychiatry, is. Very simply, it’s an attempt to understand the roots of mental and psychological disorders through the principles of Darwinian evolutionary science—that is, evolution by natural selection. The starting point in Darwinian sciences is that all living organisms originated and evolved through purely natural processes, and the human species is no exception. In evolutionary science, humans are considered a species of the great apes (Great Apes), and human physical and psychological traits emerged and were shaped by natural evolutionary factors that led to the selection of these traits because they were more successful than the alternatives in survival and reproduction during the deep evolutionary history of the human species.

Through research in paleontology and genetics, we now know that humans shared a common ancestor with chimpanzees around seven million years ago and with gorillas around ten million years ago. However, this doesn’t mean we evolved from chimpanzees or gorillas; it means we had a common ancestor with the chimpanzee lineage. This common ancestor went extinct but gave rise to two separate lineages—one leading to humans and the other to modern chimpanzees. It’s a common misconception that we evolved from monkeys. This is incorrect, rather we share a common ancestor with monkeys, and we share a common ancestor with all living organisms, because we know that all living organisms existing today originated from a single ancestor that lived on Earth about three and a half billion years ago. So, it is not just monkeys—some mock the idea of how we could have evolved from monkeys. The reality is that we evolved from organisms much simpler than monkeys.

It’s important to note that during these seven million years since our divergence from the common ancestor with chimpanzee lineages, around 23 hominin species appeared. To date, scientists have identified 23 hominin species in the human lineage before Homo sapiens (modern humans), the only human species that survives in the world today. All those other species went extinct, leaving just one human species; ourselves. Thus, viewing psychological traits as having arisen due to selective evolutionary factors to serve functions that aid survival and reproduction is a concept shared between evolutionary psychiatry and evolutionary psychology.

However, the realization that psychological traits were shaped because they were more successful in serving survival and reproduction helps us understand the reasons for their existence in a different or deeper way. In the view of evolutionary psychiatrists, you cannot fully understand mental disorders without understanding the function of the system they arise from that is shaped by natural selection. Therefore, evolutionary psychiatry and evolutionary medicine in general can pose questions about the biological roots of diseases and disorders, because our focus isn’t just on the physiological function of traits but also on how they become disrupted and turn into burdens. This is a domain shared across all of medicine, but evolutionary medicine examines these traits through questions that go beyond what general medicine typically asks.

An example of this deeper understanding is what is referred to as Tinbergen’s Four Questions, which I consider the cornerstone of evolutionary sciences, and many share this view. Nikolaas Tinbergen, one of the prominent figures in 20th-century biological sciences, won the Nobel Prize alongside two others—a rare instance of someone receiving the Nobel Prize through evolutionary thinking. He proposed an understanding of causality and how evolutionary sciences help us understand causality more deeply in the field of life sciences. I won’t delve into the details of these principles, but I wish to highlight them as a headline, and listeners/viewers can look into them further. This deeper understanding of causality is one of the benefits of applying evolutionary sciences to medicine and psychiatry.

One evolutionary concept that explains the existence of certain disorders is the concept of “mismatch” between a human trait that evolved in the ancestral environment and modern environmental conditions. Without adopting a Darwinian stance, that appreciates and recognises that traits are shaped through an evolutionary selective process that is optimal for a given set of environmental conditions it will not be possible to conceive of the concept of mismatch. Mismatch can only be understood through an evolutionary lens.