Evolutionary Medicine

Definition:


Evolutionary medicine or Darwinian medicine is the application of modern evolutionary theory to understanding health and disease. It is not a new specialty or method of practice or critique of medicine but consists of the intersections whereevolutionary ideologies bring something new and useful to the medical profession, and where medical research offers new insights, questions, and research opportunities for evolutionary biology[1]

The four principles are:[2]

  1. Organisms are bundles of compromises shaped by natural selection to maximize reproduction, not health. They are thus full of unavoidable tradeoffsand constraints.
  2. Biological evolution is much slower than cultural change, much disease arises from the mismatch of our bodies to modern environments.
  3. Pathogens evolve much faster than we do, so infection is unavoidable.
  4. The idea that common inheritable diseases are caused by a few defective genes is usually incorrect, rather, multiple genetic variants interact with environments and other genes during development to influence diseasephenotypes

The structure of evolutionary medicine is still defined mainly by the different contributing disciplines. Genetics, paleontology, microbiology and immunology, ecology, reproductive medicine, cancer research, physiology, anatomy, behavioral biology, epidemiology, anthropology, and clinical medicine that all pursue evolutionary questions using somewhat different traditions and methods.[3]


The Human Body a Machine?


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An evolutionary perspective fundamentally challenges the prevalent but fundamentally incorrect metaphor of the body as a machine designed by an engineer. Bodies are vulnerable to disease – and remarkably resilient – precisely because they are not machines built from a plan. They are, instead, bundles of compromises shaped by natural selection in small increments to maximize reproduction, not health. Understanding the body as a product of natural selection, not design, offers new research questions and a framework for making medical education more coherent. However, because they are products of evolution, bodies are very different from machines. A deep understanding of the body as a body is perhaps evolution’s greatest single contribution to medicine. Machines are designed by an engineer to serve a human purpose. Blueprints define the ideal type, and manufacturer.When a defect is discovered, engineers change the design. Bodies are not designed; they are shaped by natural selection. There is no blueprint, no ideal type. Variation is intrinsic. There is no normal genome. There is no normal body. There is no separate manufacturing facility; there is just the process of development – genes interacting with environments to create adult forms. The process involves some chance factors, and also adaptations that monitor the early environment and shift development in ways that adjust the adult form to a particular environment. Some traits, such as a birth canal that passes through a narrow circle of bone, cause problems for the species. But there is no engineer with a drawing board to go back to. Rerouting birth via the abdominal wall would work better, but the intermediate stages between that and the current route would not work, so the system stays suboptimal. Bodies are bodies shaped by selection, not machines designed by intelligence. Giving up the machine metaphor gives medicine a stronger foundation in biology.[4]

Important Researchers


Randolph M. Nesse, George C. Williams, Paul W. Ewald, James McKenna and, Wenda Trevathan


History


Evolution and medicine started an immature romance in the late 19th century that broke up amid violent recriminations in the early 20th century. Thereafter, the relationship remained distant until the partners were reintroduced on a more mature basis by Nesse and Williams’s recent book, Why We Get Sick: The New Science of Darwinian Medicine. The book stimulated a symposium in Switzerland in 1996, out of which came a book edited by Stearns that, together with another book Evolutionary Medicine edited by Trevathan et al. raised interest, connected to the existing body of basic research, and provided materials for the courses that were starting to be offered. Evolutionary medicine is a highly interdisciplinary field, and anthropologists have played important roles in directing attention not only to evolutionary processes but also to sociocultural and sociopolitical effects on human health. The opportunities are large in the clinic, the research laboratory, and the classroom.[5] [6]

Biological anthropologists have been contributing to what is now referred to as evolutionary medicine for more than a half century, although the phrase itself began to be widely used only in the early 1990s. Three topics in which anthropological contributions have been especially significant include nutrition, reproductive health, and chronic disease. A major focus in nutrition and reproduction is the health consequences of evolved biology in the context of contemporary diets, lifestyles, and contraceptive practices seen in industrialized nations.[7]


Evolutionary Perspective and Medical Practice


Evolutionary biology is an essential basic science for medicine, but few doctors and medical researchers are familiar with its most relevant principles. Most medical schools have geneticists who understand evolution, but few have even one evolutionary biologist to suggest other possible applications. Medically evolution helps to make sense of new genetic data. Why, for example, do genes that predispose to asthma persist? Why, for instance, does bilirubin exist? Who would have thought it was to slow aging?Some evolutionary technologies, such as population genetics, serial transfer production of live vaccines, and phylogenetic analysis, have been widely applied. Other areas, such as infectious disease and aging research, illustrate the dramatic recent progress made possible by evolutionary insights. In still other areas, such as epidemiology, psychiatry, and understanding the regulation of bodily defenses, applying evolutionary principles are just beginning to be explored.Many medical students do not even accept the theory of evolution. Most medical students get two or more years of basic science education, including embryology, biochemistry, anatomy, histology, and physiology, and many get a genetics course from a professor who knows evolutionary biology. However, we know of no medical school that teaches a course in evolutionary biology as a basic medical science, and none that requires evolution as a prerequisite. Our teaching experience confirms that few doctors have a chance to learn the principles of evolutionary biology most useful for medicine. Medical professionals learn other basic sciences not because they are useful everyday in the clinic, but because they provide a crucial depth of understanding and a framework for organizing the myriad facts in which the mind otherwise drowns. Knowing the mechanisms and laws of acid–base balance gives a physician the perspective needed to apply formulas in the clinic. Evolutionary biology offers the same sort of help, but on a much larger scale. Instead of phenomena as specific as acid–base balance, evolution helps doctors make sense of why a disease exists at all, what environments increase the risk, and how treatments work. It has direct applications to medical research, but it also provides an otherwise missing paradigm for understanding why our bodies are vulnerable to disease.[8]

Evolutionary Medicine Related Concepts and Examples

Infectious disease
parasites
immune system evolution;
Paleolithic nutrition and physical activity
chronic diseases in the present
Evolution of skin color
rickets


Case Study: Thrifty Genotype vs. Thrifty Phenotype


The basic premise of the thrifty gene hypothesis is that certain populations may have genes that determine increased fat storage, which in times of famine represent a survival advantage, but in a modern environment result in obesity and type 2 diabetes. The concept finds support among high type 2 diabetes susceptibility populations, such as North American Indians and South Pacific islanders. However, in some developing communities (e.g., Black South Africans) the thrifty phenotype hypothesis of intra-uterine malnutrition causing insulin dysfunction seems a better explanation, but this remains a contentious issue. Several genes have already been identified as candidates for the thrifty genotype.[9]


VIDEO: HIV Immunity Evolution


Video link: HIV immunity evolution on PBS



Additional Resources

1) Evolutionary Medicine and Health: New Perspectives. Edited by Wenda R. Trevathan, E. O. Smith and James McKennahttp://www.oup.com/us/catalog/general/subject/Anthropology/?view=usa&ci=9780195307061

2) Relevance of Evolution: Medicine by the Understanding Evolution team http://evolution.berkeley.edu/evolibrary/article/medicine_01//

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References


  1. ^ Stearns, S. C., Nesse, R. M., Govindaraju, D. R., and Ellison, P. T. (2010) Colloquium Paper: Evolutionary Perspectives on Health and Medicine. Proceedings of the National Academy of Sciences 107(suppl_1):1691-1695.
  2. ^ Stearns, S. C., Nesse, R. M., Govindaraju, D. R., and Ellison, P. T. (2010) Colloquium Paper: Evolutionary Perspectives on Health and Medicine. Proceedings of the National Academy of Sciences 107(suppl_1):1691-1695.
  3. ^ Nesse, R. M. and Stearns, S. C. (2008) The Great Opportunity: Evolutionary Applications to Medicine and Public Health. Evolutionary Applications 1(1):28-48.
  4. ^ Nesse, R. M. and Stearns, S. C. (2008) The Great Opportunity: Evolutionary Applications to Medicine and Public Health. Evolutionary Applications 1(1):28-48.
  5. ^ Nesse, R. M., Bergstrom, C. T., Ellison, P. T., Flier, J. S., Gluckman, P., Govindaraju, D. R., Niethammer, D., Omenn, G. S., Perlman, R. L., Schwartz, M. D., Thomas, M. G., Stearns, S. C. and Valle, D. (2009) Colloquium Paper: Making Evolutionary Biology a Basic Science for Medicine. Proceedings of the National Academy of Sciences 107(suppl_1):1800-1807.
  6. ^ Stearns, S. C., Nesse, R. M., Govindaraju, D. R., and Ellison, P. T. (2010) Colloquium Paper: Evolutionary Perspectives on Health and Medicine. Proceedings of the National Academy of Sciences 107(suppl_1):1691-1695.
  7. ^ Trevathan, W. R. (2007) Evolutionary Medicine. Annual Review of Anthropology 36:139-154.
  8. ^ Nesse, R. M. and Stearns, S. C. (2008) The Great Opportunity: Evolutionary Applications to Medicine and Public Health. Evolutionary Applications 1(1):28-48.
  9. ^ Joffe, B. and Zimmet, P. (1998) The Thrifty Genotype in Type 2 Diabetes: An Unfinished Symphony Moving to its Finale? Endocrine 9(2):139-141.