Why do we age? Why is congestive heart failure so common? Why do so many of us wear glasses? Why is there a menopause? Why must we sleep? Why do we get febrile when infected?
If you are like most medical students, trainees, or physicians, your first responses to these intriguing questions is to think about pathophysiologic answers. We are drawn to underlying questions of how the mechanism might work. These proximate, mechanistic explanations form the conceptual and cognitive framework for our learning, practice, and research in medicine.
But they only tell half the story.
To learn more, join the
Evolution and Medicine Community on the
http://connect.sgim.org website.
The aim of this Community is to build a network of SGIM members who share a fascination with the view of health and illness through an evolutionary lens. Through this lens, the very nature of questions one can ask shifts from proximate “what” questions about pathophysiologic mechanisms to ultimate “why” questions about evolutionary mechanisms (natural selection, drift, tradeoffs, kin selection, phylogenetic explanations, etc). I think you will find it fascinating to expand your paradigm from what is going on in my patient to how did my patients get this way in the first place and why are humans still vulnerable to the diseases they get.
Medicine is based on biology and biology is based on evolution but medical education and research rarely taps into the elegance and power of evolutionary principles. Traits and illnesses require both types of explanation - proximate and evolutionary. Else, we are practicing and teaching medicine with only half of biology.
Three cutting edge applications:
1. Evolutionary management of antibiotics. Should you always tell your patients to finish every pill in the bottle even after they feel better? In treating infections we must balance curing the patient with minimizing the selection for resistant populations. Evolutionary principles are guiding the testing of novel (evolution-proof) strategies to prolong the useful life of these vital drugs.
2. Living with cancer. The "war on cancer" metaphor suggests we must completely vanquish the enemy. While this may be appropriate for some cancer types, evolutionary biologists remind us that most tumors consist of multiple clonal populations competing for resources. By nuking tumors with overwhelming force, we select for resistant and more virulent clones, which may have been held in check by less malignant clonal neighbors. Less aggressive chemotherapy in rats has led to dramatically longer life expectancy by aiming at reducing tumor volume. We may need to rethink our metaphor and learn how to live with cancer as we do with other chronic diseases.
3. Lost friends. In the last 50 years, rates of infectious disease (TB, measles, parasites, etc) has dropped dramatically, replaced by many chronic, "auto-immune" diseases (DM, IBD, asthma, etc). Crohn's and ulcerative colitis are rare in populations with helminthic infections. After eons of coevolution, we are only recently living without our old "friends." Helminths down-regulate our Th2 immune response ("humoral" immunity against extracellular pathogens), and without them, our Th1 immune pathways ("cell-mediated" immunity against intracellular pathogens) tend to churn up. Animal and early human studies suggest that tolerable "doses" of helminths can dramatically reduce the inflammation of IBD and other auto-immune disorders.
This new SGIM Community will help us learn about these and other valuable lessons from evolutionary perspectives on health and disease.
Mark D Schwartz, MD