Selective pressures and the evolution of alternative medicine

i-e7a12c3d2598161273c9ed31d61fe694-ClassicInsolence.jpgEvery so often, real life intrudes on blogging, preventing the creation of fresh Insolence, at least Insolence of the quality that you’ve come to expect. This is one of those times. So enjoy this bit of Classic Insolence from back in November 2007 and be assured that I’ll be back tomorrow. Remember, if you’ve been reading less than two and a half years, it’s new to you, and, even if you have been reading more than two and a half years, it’s fun to see how posts like this have aged.

I wish I had thought of this one, but I didn’t. However, I never let a little thing like not having thought of an idea first to stop me from discussing it, and this particular idea is definitely worth expanding upon because (1) it’s interesting and (2) it combines two of my interests, alternative medicine and evolution. I agree with parts of the idea, but it’s not without its shortcomings. Indeed, I’d very much welcome any of the evolutionary biologists who read this blog to chime in with their own ideas.

Fellow ScienceBlogger Martin Rundkvist over at Aardvarchaeology has proposed a rather fascinating idea regarding the evolution of alternative medicine in which he argues that alternative medicine evolves according to certain selective pressures. As you may or may not know, evolution is not just for biology, but has been proposed as a mechanism in cultural memes, for example. Since alternative medicine is a cultural phenomenon, it is not unreasonable to look at such non-evidence-based medicine and hypothesize what might be the selective pressures that shape its popularity and evolution. After all, if we’re going to discourage the use of non-evidence-based medicine or even quackery, it’s helpful to understand it. We already know that alt-med terminology has evolved considerably into the current politically correct term “complementary and alternative medicine” (CAM).

Martin primarily considers what the selective pressures are on various alternative medicine modalities and comes to a startling conclusion: Namely, that the selective pressure on such modalities is primarily to select for ineffective treatments. He bases this on two primary forms of negative selection. First, he hypothesizes, there will be selective pressure against modalities that cause obvious harm. According to this concept, such modalities will tend to be eventually recognized as harmful and shied away from by alternative medical practitioners due to fear of lawsuits and government regulations. The second form of selective pressure will come from conventional medicine. In essence, alternative medical therapies that can be shown to have a reasonable degree of efficacy will risk being co-opted by us “conventional” practitioners of evidence-based medicine and thus taken out of the armamentarium of alternative practitioners, whose setting themselves apart from mainstream medicine is very important to their livelihood. This leads Martin to observe that homeopathy is the ultimate CAM therapy:

So, there is evolutionary pressure on alternative therapies to achieve near-zero effect. This is why homeopathy is still around: its main method being the administration to patients of small amounts of clean water, it’s uniquely suited to surviving indefinitely in the alternative-therapy biotope. Homeopathic remedies can neither harm nor benefit patients.

This is a fascinating and lucid insight. Clearly it has some merit. However, it is incomplete. The reason, I would argue, is that the negative selective pressures Martin identified are almost certainly not as potent as he thinks they are, as evidenced by how rare it is for an alternative medical therapy to actually go “extinct.” Indeed, I would argue that selection against harmful or potentially harmful remedies is actually fairly weak and perhaps even nonexistent. After all, black salve is still around after many decades, if not hundreds of years, and it can produce some truly horrifying complications (not for the squeamish). Even though the FDA banned importation of black salve products and they can be demonstrably harmful, they are still around and show no sign of disappearing. Another example is Laetrile. Multiple well-designed clinical trials demonstrated that Laetrile is ineffective against cancer, and it has the well-known potential complication of cyanide toxicity. It, too, shows no signs of disappearing. Of course, perhaps the most popular ineffective CAM therapy that has potentially deadly complications is chelation therapy, which remains widely used among CAM practitioners to treat cardiovascular disease and autism, despite of the extreme biological implausibility of the argument that it should work for either condition and despite there being no good evidence that it does. Indeed, there was even a well-publicized case of an autistic boy who died as a result of hypocalcemia as a result of chelation therapy for autism causing a fatal cardiac arrhythmia. His quack–I mean doctor; no, I mean quack–Dr. Roy Kerry is only now being brought up on charges for his negligence and quackery.

No, there are lots of potentially harmful CAM modalities out there that show no signs of going away.

Let’s look at the flip side of the negative selection, co-optation of “effective” alternative therapies into mainstream medicine. Once again, this is probably a weaker negative selective force than it might seem. Herbal medicines, for example, are probably the most common of the CAM-type modalities to show some evidence of efficacy in randomized clinical trials. This is mainly because they are drugs. Impure and dirty drugs with widely varying levels of active ingredient from lot to lot, but drugs nonetheless. The problem for the co-optation of these drugs by conventional medicine is that practitioners of scientific medicine do not like unpredictability in their drugs. They like drugs with a predictable effect; herbal medicines “in the raw,” so to speak, do not fit the bill, particularly when pure pharmaceutical alternatives that lack the contamination and unpredictability of herbs exist. Even if conventional medicine co-opts an herb, for example, it is usually in the form of the pure active ingredient purified from that herb. For example, if you have breast cancer, you could try to chew on the bark of the Pacific Yew tree for its anticancer properties, but you’d be a whole lot more likely to do better if you took pure Taxol derived from that bark–and took it intravenously. The example of Taxol also suggests that once conventional medicine co-opts an herbal or plant-based remedy, it usually does not supplant the original alternative therapy. After all, all of the “natural goodness” has been extracted from it during the purficiation of the active ingredient! CAM mavens would often rather take the raw herb or the herb chopped up and compressed into an herbal pill because it’s more “natural.”

As for other non-herbal CAM therapies, even when they’re co-opted by modern medicine (although it’s often arguable whether conventional medicine or CAM did the coopting), often an “alternative” version remains. The scientific version will be stripped of all the woo, while the “alternative” version will retain it. Think massage therapy and perhaps even chiropractic, which, as I’ve said before, stripped of its woo is nothing more than physical therapy with delusions of grandeur in the form of claims of being able to cure all manner of illnesses that have nothing to do with the spine or the musculoskeletal system.

Finally, there is one last aspect of Martin’s concept that argues against it. Martin states:

Evidence-based medicine, alternative medicine and weaponry change through time because of selection pressure. This means that they evolve and produce a fossil record of discontinued methods and therapies.

Here’s the problem: There actually is no “fossil record” of discontinued CAM methods and therapies. The reason is simple: CAM does not abandon its methods, regardless of evidence and, to a large degree, regardless of harm. Yes, individual treatment modalities may wax and wane in popularity, but they never go away completely. They never go extinct. Think about it a bit. Can you think of a single “alternative medicine” treatment modality that’s ever been abandoned because it either doesn’t work, is too harmful, or has been co-opted by conventional medicine. I can’t. CAM is, in the words of James Randi, an “unsinkable rubber duck.” It just won’t disappear. Martin is quite correct that homeopathy, for example, has persisted 200 years despite no evidence for its efficacy. Aryuvedic medicine has persisted at least a couple of millennia, despite a similar lack of evidence. Ditto traditional Chinese medicine. Never mind that these systems were developed in a time when very little was known about how the body actually works and are infused with spiritual and religious beliefs. They are still used my many millions, if not billions, of people worldwide. They have left no “fossils.” Of course, as in evolution in biology, this selection, applied over long periods of time, may ultimately eliminate such modalities, but if I were somehow able to call the Doctor to give me a ride in his TARDIS a couple of hundred years in the future, I bet that virtually all of these CAM modalities would still be in use. Part of the reason, I suspect, is that, as Martin pointed out, most CAM modalities do little; there is usually no CAM modality that can supplant existing modalities.

In any discussion of the evolution of CAM, I would be remiss not to look at its primary competition for resources (i.e., patients) in the ecosystem of medicine, namely scientific, evidence-based medicine. EBM has been hugely successful in many areas. Indeed, it can be said to have driven back CAM to a much smaller “ecological” niche than it once occupied. These days, relatively few people rely on CAM modalities when faced with a truly life-threatening illness, such as cancer. The Katie Werneckes, Abraham Cherrixes, and the Chad Jessops of the world (if the latter even had cancer), who treat life threatening cancers with high dose vitamin C, the Hoxsey concoction, or nasty, burning goo like the infamous “black salve,” respectively, are pretty uncommon. The main ecological niches for CAM these days have contracted to two areas. First are “diseases of living.” In other words, CAM has been for the most part relegated to the treatment of what are generally vague complaints that are not exactly diseases or to self-limited conditions. Indeed, one could argue that the strongest positive selective pressure for CAM modalities is how well each one gives the appearance of doing something therapeutic for such conditions, whether it actually does anything or not. In other words, how good of a placebo is it? Or is its timing or method of administration optimally adapted to correlate with the patient’s improvement anyway, allowing the confusion of correlation with causation? The better the adaptation, the more likely a CAM modality will thrive and expand.

The other remaining ecological niche for CAM, I would argue, is in serious diseases for which conventional medicine does not have much to offer. These conditions include diseases such as terminal cancer that has passed beyond our ability to treat it, as well as any manner of chronic diseases for which conventional medicine does not have a cure, such as Parkinson’s disease, chronic pain syndromes, multiple sclerosis, etc. Conventional medicine can treat and often palliate such conditions, but it cannot cure them. In this latter niche, I would argue that the primary positive selective pressure would be how well the CAM modality can inspire belief in its practitioners and hope in its users. The two are related, of course; the more the practitioner believes in the modality the more he or she can sell the patient on it.

Of course, applying evolutionary principles to CAM only goes so far. It’s a highly complex situation, and there are a number of positive and negative selection pressures that one could postulate. Certainly, the marketplace and how much of a feel-good aspect there is to CAM therapies are important. Finally, no doubt, like evolution, there are aspects to CAM proliferation that do not depend upon selection, a CAM equivalent of genetic drift, for example. I’m not sure how far this application of these principles will take us, but I suspect that they can be used, along with other disciplines such as psychology and anthropology, to explain to some extent the insinkable persistence of these non–evidence-based therapies.

ADDENDUM:

  1. Orac: Applying evolutionary principles to alternative medicine again
  2. Steve Novella: Alternative Medicine and the Evolution Analogy