Using Evolutionary Biology in the Medical Sciences

Abstract

Evolutionary thinking applied to medical practice helps unravel the ultimate causes of a disease and improves diagnostics and therapies. We ask why diseases persist during times when evolution's grip on humanity should be relaxed relative to the past, when environments were not so favorable to health. Genetic variation is central to evolutionary thinking: adaptations evolve by natural selection of inherited differences linked to survival and reproduction. Genetic diseases recur because of mutations inherited through the complex (often unknown) junction between ancestral origins, long‐term size of populations of patients' origins and histories of natural selection. Effects of mutations differ according to patients' environmental and genetic backgrounds. Some diseases persist because of mismatches between previous adaptation and modern human diets. For infectious diseases, rapid genetic change and evolution of microbes leads to emergence of new pathogens and pathogen resistance to antimicrobial drugs, and may limit the improvement of public health interventions (design of vaccines providing long‐lasting protection from human‐adapted pathogens like influenza and malaria). A key recognition is that evolution is dynamic, and both patients and pathogens vary and may change. Disease represents a convergence of evolutionary histories: patients' inherited mutations and adaptations, and microbes' infection, pathogenicity and transmission.

Key Concepts

  • Evolutionary thinking in medicine distinguishes between proximate and ultimate evolutionary causes of disease.
  • Mutations that cause disease in modern times may have been adaptive in the past, and thus code for traits that are maladaptive (mismatched) in modern environments.
  • Weak selection on diseases related to aging explains their persistence in modern times, especially as post‐reproductive longevity increases.
  • The evolutionary potential of microbes ensures that infectious diseases will evade therapies and vaccines in the future.
  • The evolutionary potential of microbes also makes it likely that novel infectious diseases will emerge from reservoirs in wild animal populations.
  • Medical research on therapies and diagnostics depends on testing animals most closely related and thus most similar to humans.
  • Individual patients' presentation of disease will depend on complex interactions at the convergence of patients' ancestry (genetic legacies), the evolutionary history of pathogens to which they are exposed, and the environmental context where the patients and pathogens meet.
  • Racial identity (even self‐identity) is not equivalent to ancestry, and while understanding individual ancestries (family histories) may improve medical practice, racial differences are not generally predictive for diagnosis and therapies.

Keywords: adaptation; environmental mismatch; fitness trade‐off; genetic disease; infectious disease; mutation; natural selection; pathogen evolution

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Further Reading

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Antolin, Michael F(Apr 2017) Using Evolutionary Biology in the Medical Sciences. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0005846.pub3]