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Evolutionary Medicine

I have been asked to review a pre-publication proof of a book that will be published in May 2009: Evolution Rx: A Physician’s Guide to Harnessing Our Innate Capacity for Health and Healing by William Meller, MD. It offers “a primal yet radical new view of why we act and feel the way we do, why we get sick and how we heal. This new perspective, known as evolutionary medicine, looks at how our Stone Age ancestors lived, loved, got sick and got well over millions of years, which leads to guidelines for living longer healthier and happier lives today.”

He says we are the way we are because that’s what it took to adapt and survive throughout our evolutionary history. To some extent, that’s true, but that’s not the whole story. Sometimes we are the way we are because of an accident of evolutionary history that had no bearing on survival. Sometimes we are the way we are because a useless trait was linked to a useful one and came along for the ride – what Stephen Jay Gould referred to as “spandrels.”

The problem with evolutionary explanations is that we can never know for sure if they are true. We may be inventing “Just So Stories” like Rudyard Kipling’s “How the Camel Got His Hump.” Our explanation may seem perfectly reasonable but we may not have all the information and there may be a better explanation that simply doesn’t occur to us.

There are also pitfalls in trying to determine how our Stone Age ancestors lived. The evidence is spotty. It is tempting to think we should try to live more like they did, but that doesn’t necessarily follow. Stone Age women had fewer menstrual cycles during their lifetime because of constant pregnancies and breastfeeding – does that really mean that we should suppress menstruation in women today? Maybe, maybe not.

Meller offers reassuring explanations for various diseases and conditions, trying to show that they are good, not bad. Morning sickness protected the fetus from toxins in foods. Prematurely bald men looked wiser so were more likely to mate. Sickle cell trait protects from malaria. Pain helps prevent further injury. Injuries may be good for us by stimulating repair mechanisms that may also weed out cancer. ADHD evolved as a survival trait – people who weren’t focusing on one thing were more likely to notice a new thing like the tiger behind the bush.

He sees the consequences of evolution in his patients and he shares his insights with them.

I wanted to see if understanding their deep evolutionary past would help them when they sprained an ankle or struggled with diabetes. It didn’t take long to see the effect… patients develop[ed] an entirely new outlook… followed by positive and dramatic changes.

So he says. But he offers no evidence.

Do we really need to explain the evolutionary history of obesity, or is it enough to tell obese patients what I used to tell them: “There’s nothing wrong with you; in fact there’s something very right. If you and I were in a famine situation, you would be more likely to survive. Unfortunately when food is abundant, your calorie-conserving abilities become a detriment.”

I really can’t see a need for a separate “evolutionary medicine” since evolutionary knowledge and concepts are already an integral part of scientific medicine. Evolution helps us understand why we have a blind spot in the eye and how bacteria develop antibiotic resistance.

Much of Meller’s advice is refreshing. He rejects common myths like the need to drink 8 glasses of water a day, the need for detoxification, and the need to stretch before exercise. He shows that taking vitamins and antioxidants is likely to do more harm than good. He rejects alternative medicine’s unproven treatments. He says there is “no evidence that eating organic foods or using any detoxifying products actually improves health or prevents cancer.” He says “We play fast and loose with massive amounts of known toxins [cigarettes, alcohol], yet fret over compounds measured in parts per billion with little measurable effect.” He says so much that is in line with good science-based medicine that it makes it just that more disappointing when he slips.

He says some things that are questionable and some that are simply wrong. He says you can reduce your children’s risk of nearsightedness by encouraging a low carbohydrate diet, playing outdoors and holding books at least 18 inches away from their eyes. I could find no evidence to support any of those claims. He says the Women’s Health Initiative showed that the total death rate among women taking hormones was lower than those who didn’t. That’s just wrong: the study showed no difference in mortality between the two groups. He says the best treatment for lactose intolerance is to drink small amounts of milk regularly because this will increase your production of lactase. I couldn’t find any evidence to support that claim. He says the McKenzie back exercises are the best treatment for low back pain: most doctors disagree. I don’t even know what to make of his statement that “tuberculosis was in rapid decline, even before antibiotics, largely due to the immune-stimulating effects of sunlight.” Or “two genders exist because juggling our genes doubles our resistance to infection.” There are many other statements in the book that bother me.

The text is interspersed with boxes giving “Evolutionary Prescriptions” for various conditions. I don’t see how he can justify calling them “evolutionary” since they are mostly the conventional medical advice that everyone already follows. What is “evolutionary” about preventing cancer by not smoking, by getting a colonoscopy after age 50, by taking HPV vaccine, etc.? Other parts of his evolutionary prescriptions are fanciful, like a low carbohydrate diet and playing outdoors to reduce the risk of myopia. What is evolutionary about his advice to nap for 90 minutes after lunch, and where is the evidence that such advice improves patient outcomes?

The author is skeptical about many of the things I’m skeptical about, but I’m skeptical of some of the other claims that he accepts. Seeing everything in medicine through evolutionary glasses impresses me as more of a gimmick than as a clinically useful approach. Evolution clearly informs medical practice, but I can’t see the value of “evolutionary medicine” as a separate discipline and I can’t recommend this book.

Posted in: Book & movie reviews, Evolution

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