The Relevance of Evolution to Medicine

Writing in PLoS Biology, Catriona MacCallum offers these wise words on the subject of evolution and medicine. The article describes a conference MacCallum attended on the subject. MacCallum writes:

One reason that evolution doesn't figure prominently in the medical community is that although it makes sense to have evolution taught as part of medicine, that doesn't make it essential. As explained at a meeting on evolution and medicine I recently attended in York, United Kingdom (the Society for the Study of Human Biology and the Biosocial Society's 2006 symposium, “Medicine and Evolution”), medicine is primarily focused on problem-solving and proximate causation, and ultimate explanations can seem irrelevant to clinical practice. Crudely put, does a mechanic need to understand the origins, history, and technological advances that have gone into the modern motor vehicle in order to fix it?

You see this sort of thing a lot. Mathematics is ultimately based on axiomatic set theory, but you can have a nice long career in the subject while knowing very little about it. The foundations of a discipline are frequently irrelevant to the day-to-day practice of that same discipline. As the paragraph suggests, if you're a doctor trying to diagnose some specific problem in a patient, the pricniples of evolutionary biology are unlikely to be useful.

But diagnosing specific ailments in specific people is not the only thing doctors are called upon to do. The essay goes on to describe various ways in which evolutionary hypotheses continue to lead to prgress in medicine. Here's a typical example:

The most obvious examples of evolutionary biology's importance to medical understanding are related to infectious disease [7]. As Jon Laman (Erasmus University, The Netherlands) pointed out at the meeting, the immune system provides the perfect platform to explain the medical relevance of the exquisite evolutionary relationships between pathogens and their hosts. Understanding how virulence evolves, for example, can help predict the potential, sometimes counterintuitive (and controversial) negative consequences of imperfect vaccination [8,9]. But evolution can also tell us that the origin of HIV was precipitated by a jump across the primate species barrier [10] and enables us to predict the imminent arrival of avian flu and the mutations most likely to be responsible for that evolutionary leap from birds to humans [11]. Where epidemiological and population genetic processes occur on the same time scale, the emerging field of “phylodyamics” can also inform us about the timing and progression of pathogen adaptation more generally [12].

The relevance of evolution to medicine is, however, much broader. Participants at the York meeting discussed not only how vulnerability to cancer is an inevitable but unfortunate consequence of imperfect human engineering and natural selection (Mel Greaves, Institute of Cancer Research, UK), but how life history theory can potentially explain patterns of pregnancy loss (Virginia Vitzthum, Indiana University), how a comparative approach applied to different human cultures and different primates can improve rates of breastfeeding (Helen Ball, University of Durham), whether clinical depression has an adaptive origin (Lewis Wolpert, University College London), and if suicide attempts are really just evolutionary bargaining chips in intense social disputes (Ed Hagen, Humboldt University).

Interesting stuff. Since medicine can be thought of as applied biology, and since it is impossible to reallyunderstand why biological organisms have the properties they do without taking evolution into account, it's hard to see how evolution could possible be irrelevant to medicine. Sure, in many circumstances you can get by without it, just like you can drive a car without understanding how it works. But you will never see the biological big picture without evolution.

Sadly, the essay ends on a distressing note:

Ironically, the hardest task in adding evolutionary/Darwinian medicine to medical curricula may well be soliciting support from medical students. Although Paul O'Higgins thought a comparison of the brachial plexus to the pentadactyl limb was helpful, not all his students agreed--complaints were lodged that he was forcing evolution on them. That lack of support was also reflected in the participation of only three medical students at the York meeting (albeit enthusiastic ones), despite being widely publicized. It is not clear whether this is because medical students are more overburdened than most or because of a more deep-rooted resistance to the subject, reflecting wider political and religious prejudice against evolution. But evolutionary medicine isn't and shouldn't be controversial, and the best way to challenge prejudice is through education. As the oft-quoted Theodosius Dobzhansky wrote in 1973, “Nothing in biology makes sense except in the light of evolution” [15]. The time has clearly come for medicine to explicitly integrate evolutionary biology into its theoretical and practical underpinnings The medical students of Charles Darwin's day did not have the advantage of such a powerful framework to inform their thinking; we shouldn't deprive today's budding medical talent of the potential insights to be gained at the intersection of these two great disciplines.

I suspect that a lot of those medical students who complain at the mere mention of evolution are not people who will actually attain their medical license. Alas, some of them will...