Medicine and evolution, part I: Introduction

Longtime readers of this blog may have noticed that, since my move to ScienceBlogs six weeks ago, I haven’t written nearly as much about evolution or intelligent design as I used to on the old blog.. There are probably at least several reasons for this. For one thing, lots of other topics have forced their way to the forefront of my attention, including more autism quackery by the Geiers, a politically oriented medical journal that is anything but scientific, the fire at The Holocaust History Project, applying science to green tea, and a variety of other things. Also, in light of the Dover decision in December, there didn’t seem to be as many reasons to write about intelligent design. Finally, now that I’m firmly and happily ensconced in the ScienceBlogs collective, my blogging about evolution seems a bit superfluous, given that there are others in the collective (PZ, Evolgen, Afarensis, etc.) who are more knowledgeable and widely read about evolution than I am.

Then, a few weeks ago, I saw an article in Science (that PZ and others blogged about) entitled Medicine Needs Evolution. In a brief editorial, Randolph M. Nesse, Stephen C. Stearns, and Gilbert S. Omenn explained better than I had seen in a long time exactly why evolution is critical to modern molecular medicine, pointing out several examples of how evolution helps us understand physiology and human disease better. They concluded with this clarion call:

What actions would bring the full power of evolutionary biology to bear on human disease? We suggest three. First, include questions about evolution in medical licensing examinations; this will motivate curriculum committees to incorporate relevant basic science education. Second, ensure evolutionary expertise in agencies that fund biomedical research. Third, incorporate evolution into every relevant high school, undergraduate, and graduate course. These three changes will help clinicians and biomedical researchers understand that both the human body and its pathogens are not perfectly designed machines but evolving biological systems shaped by selection under the constraints of tradeoffs that produce specific compromises and vulnerabilities. Powerful insights from evolutionary biology generate new questions whose answers will help improve human health.

Indeed. Reflecting on the role of evolution in modern medicine and getting into occasional conversations with colleagues that drifted towards evolution, I came to the hard-to-believe (to me, at least) realization that I’m probably more knowledgeable about evolution than the vast majority of physicians that I interact with. It could be because one of my major research interests involves studying homeobox genes, the understanding of which requires understanding a fair amount of evolution and how gene duplication can produce new genes with new functions. It could just be the inherent scientific geek in me that finds evolution a fascinating topic, leading me to read a lot about it and seek out scientific papers about evolution that other physicians would tend to ignore. Whatever the reason, I’ve come to the conclusion that I probably know more and think more about evolution than at least 95% of physicians. The sad part is, I’m nowhere near to being any sort of expert on evolution. Certainly I’m nowhere near as knowledgeable as the ScienceBloggers I mentioned above. Consequently, my conclusion that I know more about evolution than most other doctors isn’t really saying much. Even more sad is that I’m comparing myself to academic physicians, not community doctors, who are in the trenches doing their best to treat patients and tend to concentrate on science and studies in a very practical manner, paying attention mainly to work directly applicable to how they treat patients.

Given that I work in a cancer center, you would think that there would be more than superficial attention paid to evolution. Many of the physicians that I’m referring to are academic medical oncologists, after all, and the development of tumor resistance to chemotherapy and other treatments is a classic example of natural selection at the cellular level, just as the development of antibiotic resistance by microorganisms is at the organism level. Consequently, I’m surprised how rarely mention is made of natural selection and evolution other than in a very superficial manner, as in “Chemotherapeutic agents select for resistant clones” or “the genetic instability of tumor cells means makes the emergence of resistance almost inevitable.” That is not to say that there aren’t a lot of really brilliant medical oncologists and scientists studying chemotherapeutic drug resistance both at my institution and all over the world and discovering all sorts of very clever and novel ways of trying to prevent its development. There are, because the development of resistance to chemotherapy by cancer cells is one of the most critical and important problems that must be overcome if we are ever to conquer cancer. It’s just that most of them tend to be studying the small picture at the individual gene and protein level, rather than by probing evolutionary mechanisms that might be responsible. Similarly, we spend a lot more time how specific mutations in various genes can predispose to cancer and much less time asking what evolutionary selection mechanisms maintain such otherwise deletorious alleles at a certain level in the population. The use of whole genome gene expression profiling is starting to change that, but for the most part expression profiling is still used to identify individual candidate proteins for roles in drug resistance.

Nesse, Stearns, and Omenn correctly point out that “training in evolutionary thinking can help both biomedical researchers and clinicians ask useful questions that they might not otherwise pose.” Why, then, is so little attention given to evolution in medical school, residency, and fellowship training? A lot of it has to do with with the fact that physicians are by nature more practice-oriented. We want to develop new therapies to help patients as soon as possible and sometimes neglect the big picture or long view in our zeal to accomplish this goal. However, with the development of very powerful new molecular tools and the the completion of the Human Genome Project, understanding how evolution contributes to human predisposition to various diseases or the ability to fight off certain pathogens is finally coming within reach. Yet, we will not realize these goals if the situation remains as described by Nesse et al:

Although anatomy, physiology, biochemistry, and embryology are recognized as basic sciences for medicine, evolutionary biology is not. Future clinicians are generally not taught evolutionary explanations for why our bodies are vulnerable to certain kinds of failure. The narrowness of the birth canal, the existence of wisdom teeth, and the persistence of genes that cause bipolar disease and senescence all have their origins in our evolutionary history.

Twenty years ago, when I was studying anatomy, physiology, histology, and medical biochemistry in medical school, evolution was rarely mentioned, and then usually only in trite and simplistic examples. As far as I can ascertain, at my medical school at least, the situation is no better today. It thus became clear to me that I could still discuss evolution here at ScienceBlogs without being redundant to what my fellow SB’ers are writing if I tried to limit my writing about to the interface between evolution and medicine. To that end, with this post I’m starting a series called Medicine and Evolution. That is not to say that I won’t take swipes at creationists every now and then or wander afield into more general topics related to evolution from time to time, but for the most part, when I blog about evolution, it will be restricted to this aspect of it. By doing this, I’m hoping both to inform readers just how much evolution impacts how we understand human disease and physiology and educate myself about more complex aspects of evolution than I have before.

So, what can you expect in this series? For one thing, I don’t plan on adhering to any sort of fixed schedule (like, for example “evolution Friday” or something like that). Rather, I will add to the series whenever something relevant to it catches my fancy. The first post that I have mostly written (and which may even appear as early as tomorrow if I can find time tonight to do some editing and add a photo and some links) will concern a startling example of how evolutionary thinking can lead to new insight to human disease. After that, I’ll play it by ear, depending upon what I come across that I can fit into this theme. I do have at least one additional post in this series already planned for sometime next week on a topic I mentioned in the comments of another blog a few weeks ago.

I may even take requests.