Attaining a deep understanding of this general

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Unformatted text preview: framework for organizing medical knowledge from other basic sciences. Attaining a deep understanding of this general framework is a worthy learning objective, because much of the power of evolutionary thinking in medicine comes from its ability to foster integrative thinking about our bodies as products of evolutionary processes. Providing a Rationale for Evolutionary Content in Medical Education The relevance of evolutionary biology in medical education is by no means universally recognized. Medical school deans and other educators often ask for evidence that knowledge about evolutionary biology will improve the effectiveness of healthcare professionals. A simple response is to cite direct applications. For instance, doctors need to understand the evolution of antibiotic resistance, methods for tracing pathogen phylogenies, how selection shaped mechanisms that regulate protective responses such as pain and fever, and the intimate connections between evolution, environment, and diseases of aging. However, limiting the discussion to such direct applications sells short the utility of evolutionary biology in medicine. Much basic science education in medicine is required, not because it has direct daily applications, but because it is essential for understanding the body and disease. As summarized in overarching principle 2 in the AAMC-HHMI report, “The principles that underlie biological complexity, genetic diversity, interactions of systems within the body, human development, and in uence of the environment guide our understanding of human health, and the diagnosis and treatment of human disease.” We require competence in calculus, physics and chemistry, not because they are needed every day in the clinic, but because physicians with competence in these areas will better understand the body and will make better medical decisions. For instance, most medical schools provide an extensive course on developmental biology because understanding how a zygote develops into an adult organism is an important foundation for understanding the body in general and deviations related to disease. Understanding how natural selection and other evolutionary processes have shaped the body and its components across evolutionary time is equally valuable. Like developmental biology, it describes patterns of development that explain why the body is the way it is and why certain aspects leave us vulnerable to diseases. So far, however, no medical school teaches evolutionary biology as a basic science comparable to embryology. The large-scale structure of evolutionary applications in medicine can be organized into 10 areas by intersecting the two sub elds of evolutionary biology (phylogeny and adaptation) with ve different targets of selection: human genes, human traits, pathogen traits, pathogen genes, and somatic cell lines such as those in cancer and the immune system (26). Some of these areas are well developed and extensively taught. For instance, population genetics is the foundation for all evolutionary approaches to disease, and phylogenetic methods are widely Nesse et al. applied to pathogen evolution. Others are less well developed. For instance, asking questions about why selection has left the body vulnerable to disease is a newer enterprise that offers methodological challenges, and opportunities for deeper understanding (40, 49, 50). General recommendations like those above provide a foundation for more speci c suggestions for about what would be taught, when, and how. The AAMC-HHMI report eschews course recommendations in favor of suggesting speci c competencies and learning objectives. We follow this same format, expanding on occasion to illustrate how physicians who master speci c learning objectives will practice superior medicine. Premedical Competencies Learning objective 1 for the evolution competency in the AAMC-HHMI report requires students to be capable of explaining “how genomic variability and mutation contribute to the success of populations.” This is a valuable objective, but its implementation requires sophistication to avoid confusion. The wording could lead some to think that mutations exist to speed evolution or that the evolutionary explanation for maintained genetic variation is well understood, when it is actually an issue of intensive study in evolutionary biology, as illustrated by articles by Valle and Eyre-Walker (51) and Houle (52) in this colloquium. Variation is only the raw material; selection does the work, and drift brings added complications. Also, although the success of populations is important, one of the great achievements of 20th-century evolutionary biology is recognition that selection generally acts to maximize bene ts to individuals and their genes, not species or populations (53, 54). The other learning objective, “explain how evolutionary mechanisms contribute to change in gene frequencies in populations and to reproductive isolation,” encompasses a breadth of important material. Neither of these learning objectives focuses expl...
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