Medicine and Evolution, Part 7: The theory that dare not speak its name?

I’ve written quite a bit about the role of the theory of evolution in medicine, including how it can be used to better understand disease processes such as cancer and sleeping sickness. I’ve also lamented the woeful state of knowledge about evolution that is possessed by all too many medical students and physicians, most recently taking to task an orthopedic surgeon named David Cook for some astoundingly ignorant statements about evolution and Dr. Geoffrey Simmons. (At least it’s somewhat comforting to know that I’m not the only one who’s embarrassed for his profession in this matter.) Clearly, no one could call me proud of the state of education about evolution among my fellow physicians. However, I think a bit too much is being made of an article that was recently published in PLoS Biology entitled Evolution by Any Other Name: Antibiotic Resistance and Avoidance of the E-Word:

The increase in resistance of human pathogens to antimicrobial agents is one of the best-documented examples of evolution in action at the present time, and because it has direct life-and-death consequences, it provides the strongest rationale for teaching evolutionary biology as a rigorous science in high school biology curricula, universities, and medical schools. In spite of the importance of antimicrobial resistance, we show that the actual word “evolution” is rarely used in the papers describing this research. Instead, antimicrobial resistance is said to “emerge,” “arise,” or “spread” rather than “evolve.” Moreover, we show that the failure to use the word “evolution” by the scientific community may have a direct impact on the public perception of the importance of evolutionary biology in our everyday lives.

Basically, the authors compared the frequency of the use of the term “evolution” in research papers dealing with microbial resistance published in evolution journals versus biomedical journals. The following chart shows what they found:


In essence, medical journals use the term “evolution” far less in reference to the development of microbial resistance to antibiotics than journals in evolutionary biology do. My fellow ScienceBlogger Mike the Mad Biologist sees this as evidence that the medical world avoids the use of the term “evolution.” Meanwhile, not surprisingly, our “friends” at “intelligent design” creationist Bill Dembski’s echo chamber call the paper a lament that there’s “not nearly enough pro-evolutionary propaganda in research papers,” which is rather odd, since even ID advocates accept that microbes evolve resistance to antibiotics; they simply denigrate this process by labeling it “microevolution.”

You might think that I’d take this paper as a launching point for a rant about how this is still more evidence that physicians don’t know enough about evolution. I was tempted to do that, but then I thought about it more, and, although the article rankled somewhat, my stance softened. Also, by sheer coincidence, I first read this article on Tuesday, and yesterday the topic of Grand Rounds was microbial resistance to antibiotics, given by a full professor in the Division of Infectious Diseases. That, rereading the PLoS paper, and my own experience as a physician suggested to me potential reasons for this discrepancy. First, let’s look at how the data presented in the paper was derived. In essence, they compared papers written by evolutionary biologists to those written by physicians. To me, this makes the observation that evolutionary biologists use the term “evolution” with respect to antibiotic resistance more frequently a “well, duh!” observation. After all, the concerns of evolutionary biologists are very different than the concerns of physicians or basic scientists publishing in biomedical journals. The former will be far more concerned with the actual evolutionary mechanism by which resistance develops. The latter, on the other hand, will be far more interested in how fast it develops, what factors in the use of antibiotics cause it to to develop, and what the molecular mechanisms that explain it are that can be targeted to try to ameliorate. It’s the difference between the theoretical and the practical. Another factor to be considered is the peer review process. The peer reviewers in evolutionary biology journals will be primarily evolutionary biologists; in biomedical journals that will not be the case. Taken together, these factors would make it surprising indeed if the use of the word “evolution” and technical terms related to evolution (for example, “differential fitness,” “selection,” etc.) were anywhere near as common in the biomedical literature!

Looking at it another way, it’s the difference in how the emergence (excuse me, evolution) of microbial resistance to antibiotics appears “in the trenches.” And when you’re in the trenches, “emerge” is what resistance appears to do (actually “emerge” and “spread”). What we as physicians dedicated to infection control then want to know is: How do we prevent the emergence of antibiotic resistance and, once it has appeared, how do we slow down its growth? The authors themselves recognize another problem with their paradigm:

The frequent use of the term “emergence” rather than “evolution” seemed more to be the result of a simplified phraseology that has “emerged and spread” out of habit and repeated usage. It may also be that many nonprofessional evolutionary biologists consider “evolution” to be a rather nonspecific word meaning “gradual change,” and that “emergence” more explicitly incorporates the component aspects of the evolutionary process, namely, mutation, recombination, and/or horizontal transfer of resistance. The word “spread” may, similarly, appear to incorporate the component processes of transmission, horizontal transfer, and increase in allele frequency. While these processes are recognized by professional evolutionary biologists as important aspects of evolutionary change, biomedical researchers may have the sense that the word “evolution” is itself too imprecise.

In addition, as the lecture at Grand Rounds showed me, there’s no shying away from evolution. Selection for resistant organisms was explained, and some of the factors that result in the evolution of resistant organisms were discussed in terms of selective pressures. On the other hand, much of the lecture was the usual depressing litany about how fast resistance appears after the introduction of a new antibiotic. Some antibiotics introduced less than five years ago have already selected for resistant organisms, some of which have become widespread. It’s depressingly amazing how fast evolution can happen.

One other aspect of this paper that most of those commenting on it have failed to mention is that the news isn’t all bad. Indeed, the authors looked at the number of uses of the word “evolution” in the titles of abstracts, NSF awards, and NIH awards, and found this:


There isn’t a decrease in the use of the word “evolution” in these titles in biomedical journals. Far from it. There’s actually been a steady increase, and this is a good thing.

Basically, I think this article, while provocative, doesn’t really tell us much of anything that we didn’t already know. It’s basically the proverbial tempest in a teapot. You can read into it whatever you want. Anti-evolution “intelligent design” advocates will see it as a whine that there’s not enough “propaganda” in the biomedical literature (an utterly ridiculous comment), and those of us who are disturbed at how poor the understanding of evolution among physicians (like me) will tend to view it as more evidence of how we in medicine either don’t understand or don’t care about evolution. In reality, all this observation indicates, if it indicates anything at all, is a difference in priorities and cultures between physicians and evolutionary biologists. I do, however, agree that it would be helpful if physicians publishing in the biomedical would make an effort to write explicitly in terms of evolutionary biology whenever appropriate.