Monday, August 06, 2007

Why all medical professionals need to study evolution

As an evolutionary biologist with a 50% appointment in a medical school (in the Med. Micro. and Immunology department at U. C. Davis - my other 50% is in the Section of Evolution and Ecology on the main campus) I am somewhat dismayed by the lack of attention evolution receives in Medical Schools.

So I am starting a new thread here on my blog about why medical professionals need to understand evolutionary biology. First, there is a great site out there for people who want to learn more called the "Evolution and Medicine Network" which has links to courses, articles, books, etc.

Here are my top 10 picks for reasons medical professional need to understand evolution
  1. Antibiotic resistance. The emergence and spread of antibiotic resistance is one of the most vexing issues in medicine right now as well as one of the best studied topics in the evolution of microorganisms. Understanding how antibiotic resistance originates and spreads is fundamentally a question of evolution. The more medical professionals understand this issue the better they will be at preventing spread in hospitals and in convincing patients and the community to stop abusing antibiotics in human and animal care.
  2. Origin and spread of virulence. Not all pathogens are equal. Some are minor annoyances. Others produce really nasty outcomes. And importantly, organisms can change these virulence properties on the short term. Even more importantly, behavior of medical personnel can both influence the spread of virulent strains (can anyone say - wash your *$&% hands) and can unintentionally select for more virulent strains. Understanding the evolution of virulence is critical for making sure health care does not make things worse (see papers by Ewald for example).
  3. Vaccine use and development. Vaccines involve altering the evolutionary arms race between pathogens and hosts. It is not an intelligent design arms race. If you do not get the difference, stay out of vaccine work.
  4. Cancer origins. Cancer is in essence a analog of natural selection operating among cells within the body. Unfortunately for us, the "winners" of this selection process are those that have uncontrolled growth. Thinking of cancer in this way can help understand how to both prevent and treat it.
  5. The human microbiome. Beneficial microbes are all over us and play fundamental roles in human health. Unfortunately they are very hard to study because, well, they are small, and many cannot be grown in culture in the lab. The current ways to study them primarily involve indirect DNA based assays involving evolutionary and ecological analyses of the data.
  6. Understanding the human genome. The human genome is done (well, almost, but close enough for most uses). Now what? Well, the best way to learn about the genome sequence itself is through "phylogenomic" analyses comparing to other genomes.
  7. The relevance of animal and other models. Mouse is a useful model for some aspects of human biology but not all. Drosophila too. And even yeast and E. coli? Which aspects of human biology can be modelled by each model organism? Understanding their evolutionary history and evolutionary processes helps figure this out.
  8. Aging. Aging is in essence an unfortunate side effect of natural selection maximizing fitness by futzing with health and reproduction in the early years. Since there is little fitness cost to mutations that lead to deleterious effects when we are old, well, we are kind of screwed. But understanding the ailments associated with aging is best done with this knowledge of the efficiencies and inefficiencies of selection.
  9. The immune system. See #3 above. But this is bigger than that. The whole process of how the immune system (both the innate and the adaptive components) works both at the level of an individual and at the level of a population is an exercise in population genetics and natural selection.
  10. Pluses and minuses of high mutation and recombination rates. Many medical professionals know HIV has a high mutation rate. And some might know that recombination rates are high in some pathogens. What are the consequences of this on the pathogen biology? Read Evolution 101, or my new textbook.
  11. A bonus one. Epidemiology of infectious diseases. One of the best tools in studying the spread of infectious diseases is phylogenetic analysis - which can show how different strains are related to each other.
Just a brief tour of some of the areas that evolutionary biology informs medicine. More on this later.


  1. Catriona MacCallum8/07/2007 3:02 AM

    Completely agree - there are a couple of open access articles about this in PLoS Biology. One is an essay by Janis Antonovics et al. noting the lack of use of the actual word 'evolution' in papers about antibiotic resistance in medical journals - Evolution by Any Other Name: Antibiotic Resistance and Avoidance of the E-Word. They discuss the implications of this absence on the public perception of the importance and relevance of evolution.

    Self-servingly, I also wrote an editorial about evolution and medical education earlier this year (Does Medicine without Evolution Make Sense?), which was stimulated by this article and a meeting I attended last December in York, UK.

  2. I'd add human variation to your list. Our intra- and inter-population variation means different susceptibilities to different diseases and differing needs to maintain a healthy body.

    Also, it's important to understand that evolution does not lead to ideal phenotypes (we are not designed very well). Understanding how our flaws make us sick is important because some "flaws" may actually be important for other functions.

  3. Thanks Catriona - I had read your pub but was writing this late last night and just wanted to get something out so I did not put in too many refs.

    Actually, Michael I was not aware of Nesse so thanks.

    And RPM I agree these are both important and at some point I guess we should make a top 20 list and then really rank them. These were just the first ones that came to my head. I think the non ideal phenotype thing is perhaps the single most important concept in evolution to teach to all, including practicing biologists who think they understand evolution. I cannot tell you how many times I have tried to get lame adaptationist claims removed from papers as a reviewer or editor ...

  4. Our evolutionary history is also a good clue to various normal & abnormal anatomical structures. For example, I believe that in many cases the voice changes that sometimes reveal a lung tumor are due to the nerves for the vocal box taking a convoluted route from brain to vocal chords which goes near the lung. Tail bones, children born with webbed digits, bones of the inner ear, backwards retina -- all of which have medical relevance & all of which fit an evolutionary history.

  5. This from a book entitled Seasonally Fit, which dropped on my desk earlier this week

    "We are seasonal beings responsive to environmental cues; beings best served by living in sync with the natural ebb and flow of the daily light/dark cycle, the changing of the seasons, and in accordance with our genetic makeup. To obtain optimum fitness and health we must employ a cyclical/dynamic, not linear/static, approach to sleeping, eating, and exercising."

    It fits with the concept that modern medicine should look to our evolutionary past to understand our ills

    David Bradley Science Writer

  6. Very glad to see this new and important thread on your blog. This approach to medicine makes so much sense! If it were widely accepted, we would dramatically change the way we live on this planet which, in turn, could increase our life expectancy as a species.

    I also appreciated the other comments pointing to relevant books and articles.

  7. Antibiotic resistance and evolution - it makes so much sense, but I never put the two together until this article.

    Thanks for a great article that was easy for a non-scientist to grasp!
    : )

  8. Kim

    Thanks for the thanks. And now that I have browsed your nursing background I am curious. Did you get ANY mention of evolution in nursing training?

  9. Next you could comment on why all economic historians need to study evolution. See NYT article (8/7 Science Times - In dusty archives, a theory of affluence) on UCD Prof. Gregory Clark's recent book "A farewell to Alms".

    ...Reaction to Dr. Clark’s thesis from other economic historians seems largely favorable, although few agree with all of it, and many are skeptical of the most novel part, his suggestion that evolutionary change is a factor to be considered in history....

  10. Jess - I was reading this this morning and wondering whether to write about it ... thanks.

  11. The need of the time is spending more budget on the educational system just because of the survival of the community. this blog is really informative because it facilitate the users with the information about the environment. there are different sites that can be used to get the knowledge.we mustu be more concious and dedicate the attention toward getting the knowledge..

  12. A friend read this post and commented: "Amazing! Not a single issue raised is specific to evolution. Every one of them is easily studied and understood without any reference to evolution at all. But that won't stop misrepresenters like this or their fawning acolytes from affirming otherwise."


    Evolution and medicine

    Is evolution really necessary for medical advances?

  13. Interesting. Evolution was generally accepted in the scientific community by the 20th century. I can't recall any examples showing that the new belief about the history of life and how things can change over generations produced new benefits to health or medical practices.

    Antibiotic Resistance: Antibiotics came along in the middle of the century. Can you cite papers in which evolutionists warned that microbes would evolve resistance, before resistant cases were observed? Do you know of any real reason why belief in evolution would help with this, or do you think that creationists still believe in absolute fixity of species?

    Origin and spread of virulence: Can you cite a case where an organism became virulent because it evolved a new, more complex organelle? Was Semmelweis concerned about evolution when he championed handwashing? How about Lister and Pasteur in their efforts to control the spread of infectious agents?

    Vaccine use -- did Jenner live before or after Darwin? Are vaccines prepared by intelligent people or do scientists just grab a bunch of viruses and inject them into people?

    Cancer: " essence a analog of..." I can't think of a phrase better suited to desperately trying to stretch a concept to try to make a point.

    The human microbiome: again, the "evolutionary" analyses are no more foreign to non-evolutionists than the breeding charts and records of hybridization used by ranchers and agriculturalists.

    Understanding the human genome, The relevance of animal and other models, Aging. -- We've still got a lot to learn about these things, and there have been a number of surprises that were explained by evolution only after the fact, i.e. drawing the bull's-eyes around the arrows. The very fact that pigs, mice, guinea pigs, fruit flies, "And even yeast and E. coli" can serve as useful models for various things (and monkey and ape studies have sometimes been surprisingly misleading) indicates it's not a simple matter of evolutionary relatedness.

    The immune system. A highly complex system better understood by concentrating on facts and systems analysis rather than making up stories about how it might have come about.

    Pluses and minuses of high mutation and recombination rates: One thing is clear, even with a high mutation rate, HIV isn't evolving into something other than a virus, or even a different class of virus. This is really a variation on the point about Resistance.

    Epidemiology: see "human biome"

    So, I'm not impressed. Of course, that may be partly because I'm aware of something you did not write about: how applications of evolutionary beliefs have lead to errors and delays in understanding the human body: Listing over 100 organs as "useless vestigials," rote removal of tonsils and appendices, even forced sterilization of people with undesirable traits. I also know there are creationists who are as successful at treating people or understanding disease organisms as evolutionists. Others have made significant contributions to science. GW Carver was inspired and encouraged by his belief in creation to seek uses for peanuts and discovered many useful products could be synthesized from them. Raymond Damadian was the leading pioneer of MRI technology. Dr. Joseph Mastropaolo was the physiologist responsible for the physical training of the pilot of the first successful human-powered aircraft. Dr. John Sanborn made a major contribution to genetic research with his work on the "gene gun" technique.

    So, you might have a passion for evolutionism, but you're going to have to show something more impressive and definitive to make your case to people who aren't already committed to the cause.