Why should medical students study evolution? Here's an example.

Lately there has been a lot of posts in the blogoshere about whether doctors need to know anything about evolutionary science. Today I got drawn into this discussion over on Uncommon Descent: I posted on a thread for another reason (see Ed Brayton’s post Sal Cordova’s Rank Dishonesty for that story), and a commenter there replied to me:

You are on record as being pro Darwinist and active in promoting Darwinism. Why don’t you take a crack at supporting Darwinism here for students in general and medical students in particular. And in the process enlighten us.

Well, I spend some time responding to this person here, and in doing so told a story that I’d been thinking about writing up for the Panda’s Thumb.

So I’m going to duplicate-post my comment there as a post here. Here’s what I wrote at Uncommon Descent:

This is off the topic of my point, and the thread really, but I find that in general when ID advocates talk about “Darwinism” they are really talking about the philosophy of materialism rather than just modern evolutionary science. I support mainstream evolutionary science, and am active in promoting it, but I am not “pro-materialist” nor active in supporting materialism as a philosophy. On the contrary, I am pro-religion, and active in promoting an understanding of the nature of religion and an appreciation for the diversity of religious perspectives.

So I encourage people to keep these differences in mind.

Now to the larger question.

I am a public high school teacher. Right now I teach only calculus because I mainly have other administrative duties. Every year I explain to my students that one thing they will get from my class will be an understanding of some big ideas that will broaden their perspective on how the world works, so that even if they never do a calculus problem after they leave high school, they will benefit from having taken my course.

On the other hand, I tell them, it may turn out that some of them, or maybe just one every few years, will take what I teach them and run with it - moving on to a field where calculus is an essential tool every day for figuring out important things about the world.

And I explain that most of them will fall in between - they will be better at math and a little broader as a human being, but they will probably never use calculus outside of my calculus class.

And finally I explain that I have no way of knowing which of them might fall in these various categories, and neither do they. Teaching is somewhat like casting your bread upon the waters - I act towards all that they might be the one who will grow because of grasping a big idea, or by using the tools I give them for great good at some later time, but I have no idea about when, how and to whom the fruits of my teaching might come.

The same applies to teaching evolutionary theory to those who are studying medicine. Understanding the basics of evolutionary science broadens one’s understanding of the nature of life, and of the human beings that they will be helping. While many may not use specific aspects of evolutionary science on a daily basis, there will be others for whom the evolutionary perspective will play an important role at some point in their medical work.

Let me tell a story to illustrate.

I have a son with some difficult mental health issues, and at one time they thought he was bipolar, although now we don’t think that is true. He has never had regular sleep habits, and he also has a chronic viral infection which gets worse in the winter and better in the summer.

Therefore, I was interested in a recent article published in the Proceedings of the National Academy of Sciences, by Joseph Coyle, entitled “What can a clock mutation in mice tell us about bipolar disorder?” Coyle is a member of the Department of Psychiatry at the Harvard Medical School.

The summary of the article here says,

Bipolar disorder, also known as manic-depressive illness, is characterized by episodes of mania and episodes of depression usually interspersed with periods of relatively normal mood (1). During the manic phase, affected individuals exhibit elevated mood, irritability, increased activity, reduced sleep, hypersexuality, and increased goal-directed activities. Bipolar disorder in its various forms affects >3% of the population and is associated with a high risk for suicide, substance abuse, and vocational disability (2). Although several animal models for major depressive disorder have been developed, there are no plausible models for bipolar disorder (3). In this issue of PNAS, Roybal et al. (4) describe the results of a systematic analysis of the behavior of a mouse with a deletion of exon 19 in the Clock gene, which shows remarkable parallels to the symptoms observed in individuals in an episode of mania (1). The Clock mutant mice exhibit hyperactivity, decreased sleep, reduced anxiety, and increased response to cocaine, sucrose, and medial forebrain bundle stimulation. Furthermore, many of these behaviors can be reversed by transfection of the ventral tegmental area (VTA) dopaminergic neurons with WT Clock gene or by treatment with therapeutic doses of lithium (Li+), a commonly prescribed mood stabilizer.

Considerable evidence accumulated over the last 30 years supports the notion that bipolar disorder involves a fundamental disruption in circadian rhythms (5). The episodes of mania and depression in bipolar disorder generally develop a regular periodicity, often linked to the seasons of the year (6, 7). Within an episode, disrupted circadian rhythms including sleep–wake cycle, hormonal secretions, and diurnal variation in mood are evident (8–10). Current treatments to prevent the recurrence of episodes of mania/depression emphasize maintaining a stable diurnal pattern of activity

Well, here is a place where it is a good thing that someone in the field of medicine knows something about evolutionary science.

From the beginning, organisms have been evolving in a world which has both daily and yearly rhythms, and thus many behaviors and processes flow with those rhythms. People like my son seem to have faulty regulation of some of these processes, and that takes it toll.

Studying the genetic basis of these circadian rhythms in simpler organisms in order to perhaps some day better treat people with circadian rhythm disorders seems valuable to me.

The longer summary of the study (not online, unfortunately) is full of references to evolutionary science. Here’s an example:

The circadian clock has been shown by genetic analysis in Drosophila and mammals to consist of a time-delayed transcription–translation feedback loop (12). In mammals, a heteromeric dimer of the transcriptional activators, CLOCK and BMAL1, induces the expression of several genes by interacting with the enhancer elements of their promoters known as the E-box. These genes include Per1 (Period), Per2, Cr y1 (Cr yptochrome), and Cr y2, the protein products of which translocate to the nucleus to inhibit the activ it y of the CLOCK–BMAL1 complex, thereby repressing their own expression. Recent studies have identified a polymorphism in the 3f lanking region of Clock that is associated with more frequent episodes of mood disturbances and reduced need for sleep in bipolar subjects (13, 14). Nievergelt et al . (15) have reported a suggestive association of t wo other circadian genes, Per3 and ARNTL (BmaL1), with bipolar disorder. Mansour et al . (16) replicated the association of BmaL1 with bipolar disorder and also found an association with Timeless. Thus, clock genes are implicated as potential risk genes in this disorder of complex (non-Mendelian) genetics.

Note well that all the genes and biological pathways mentioned have first been identified and studied in simple organisms, by scientists who accept that our genetic relationship through common descent to these simpler organisms is central to this work, as well as are some of the principles of how genes mutate and the actual histories of how those mutations and their effects have been passed on through the eons.

So, as with my calculus students, students going into medicine need to learn evolutionary science. For many this will just be background knowledge that is not part of their daily practice. But for others - a critical set of others even though they may only be a few - their understanding of evolutionary science may prove to be a essential part of research or treatment that winds up making a tremendous difference.