Why Evolution?

Who decides what is “healthy” and what is “disorder”?

Le Penseur

All scientific fields are responsible for accurately distinguishing disorders from normally functioning traits. This issue lies at the core of health science, which encompasses:

    • Medicine
    • Psychiatry
    • Psychology
    • Neuroscience
    • Immunology
    • Physiology
    • Biochemistry
    • Epidemiology
    • Sociology
    • Anthropology
    • ... And many other disciplines

Science and research disciplines have largely given up the responsibility for defining health and disorder to medicine and psychiatry. There is no logical or legal reason, however, why this must be so. In fact, ascertaining how to accurately distinguish healthy states from disordered ones is an important question for any discipline or person that studies mental and physical health.

How should we distinguish between healthy states and disorders?

 Science progresses most rapidly when assumptions are tested against competing hypotheses. In the Evo-Health Lab, we use evolutionary theory to generate alternative hypotheses to the current conceptions of disorder within medicine and psychiatry.

 We use evolutionary theory for this research because the concept of health must somehow refer to the functioning of the biochemical, physiological, neurological and structural machinery of the body. These machineries (known as “traits") have an ancient evolutionary history during which they were shaped to help solve a specific problem that relates to the challenges that all living organisms face: growth, survival, maintenance and reproduction. When natural selection shapes a trait to help solve this specific problem, we refer to this trait as an “adaptation”, and the problem-solving effect as its “function”. The functions of adaptations, which we typically consider as “normal”, can be degraded over time, which can cause disorder and a decline in health. Since we consider properly functioning and problem-solving traits to be “normal”, the concepts of health and disorder can only be understood in reference to how well the body’s adaptations carry out their evolved functions.

How do we identify adaptations?

We test whether a trait is an adaptation by mapping out how it is structured and operates. Adaptation is revealed when the working parts operate in such a co-ordinated fashion to solve some problem that natural selection for the problem-solving effect is the only plausible explanation. For instance, stress response mechanisms are triggered by specific stressors (e.g., an immune response is triggered by infectious disease, but not predators), and they coordinate changes in the body that produce an adaptive response to the stressor (e.g., the activation of macrophages and the production of antibodies). Understanding a trait’s ecology (how the structure and operation of a trait interacts with the environment) is therefore important in determining whether it is an evolved stress response mechanism or a true disorder. By identifying the adaptive design of a trait, we can begin to understand where physical or psychological machinery can malfunction and cause true instances of disorder.