How can evolution help medicine?
It can give us deeper understanding about causes of and susceptibility to ailments.
It can tell us why we are vulnerable to disease which helps direct future strategies for prevention and treatment.
Will incorporating evolutionary biology transform medicine?
I get the question constantly, especially at Arizona State University, where transformation is the ideal.
My answer is “No, not directly in the short run. However, in the long run, incorporating evolutionary biology will give us a deeper understanding of disease that will transform medicine in fundamental ways.”
Medicine is a profession, increasingly a business, that tries to help individuals. It mainly makes diagnoses and provides treatments. Given those sensible goals, every medical textbook chapter about a disease has a section about its causes; what explains why some people get the disease and others don’t? That knowledge has practical implications. It is the kind of explanation a mechanic seeks when trying to find out why your car won’t start. Is it the battery? The starter? The carburetor? Or just because it is too cold today? Knowing the cause is the key to finding the solution.
However, such causes provide only one half of a complete explanation. Even for a car that won’t start, an engineer asks a different kind of question. Why is this model of car vulnerable to the problem? Is it from a poor engineering decision? Cost constraints? A manufacturing defect? Or, is it because this model was never intended to be used in a harsh cold environment? Such possibilities explain the problem at a deeper level.
An evolutionary approach encourages medical professionals to think like engineers by trying to understand these deeper causes. Why are all members of the species vulnerable to the disease. Why is the birth canal so narrow? Why can’t our bodies kill off every cancer cell? Why can’t we evolve a way to avoid all infections? Why is anxiety so common? Answers to such questions do far more than just satisfy our curiosity. They help us to understand why the body is the way it is, and why natural selection did not make it less vulnerable to disease. Answers to such questions do not guide clinical practice directly, but they are essential to clear thinking and coming up with new research ideas that will result in better strategies for prevention and treatment.
Does aging result from simple lack of selection, or because some genes that cause aging also give advantages? If the second possibility is correct, this urges caution in meddling with the mechanisms of aging. Is fever useful or just a side effect of inflammation? The answer is crucial to guide studies of how to use drugs to reduce fever. Are autoimmune disorders such as multiple sclerosis more common now because of changes in our environment? If so, we need an all out push to discover what changes are responsible? Does skin pigmentation prevent cancer or prevent breaking vitamins or both? Are panic attacks useful in some situations, or are they just products of a brain gone awry?
Every disease needs one explanation from the point of view of a mechanic, and another explanation from the point of view of an engineer. The chapters in every textbook of medicine all describe the causes of disease from the perspective of a mechanic. The section explaining why our bodies are vulnerable is missing. Providing it would add the deeper evolutionary perspective.
Asking and answering evolutionary questions about why we are vulnerable won’t transform medicine directly. Clinical recommendations should always be based on clinical studies. However, adding evolutionary biology as a basic science for medicine will transform our understanding of disease. And that deeper understanding of the causes of disease will eventually transform medicine.
President, International Society for Evolution, Medicine & Public Health
Foundation Professor, Arizona State University
Professor, School of Life Sciences, Arizona State University
Director, Center for Evolution & Medicine, Arizona State University
Sept 1, 2014