From Abracadabra to Zombies
William Meller, MD
Imagine you're watching a television program and the scene is of an archaeologist on a dig. The backdrop is a barren, sandstone colored, hilly landscape. She's crouched down, holding up a bone fragment about the size of the tip of your pinkie. The camera slowly zooms in on the little bone chip lightly clamped between her thumb and forefinger. She begins to tell you what kind of animal the bone came from, how big it was, whether it had a tail, what it ate and what ate it, how long ago it lived and what kind of environment it lived in. Pretty impressive story, but how much of it is highly probable, how much of it is wild speculation? I kept asking myself this question while reading Meller's book on evolutionary medicine. Meller mixes current scientific knowledge with evolutionary speculation. The former is valuable and interesting. I have my doubts about the value of the latter. Weeding out the trustworthy science from the hypothetical speculations isn't always easy, however. Frankly, I feel more comfortable about applying what we know from modern science in an effort to understand what diseases our ancient ancestors suffered than I do with speculation about how the evolution and adaptations of our ancestors affect human health today. The reason for my discomfort is that such writing puts an added burden on me to separate the fact from the fiction. Well, maybe 'fiction' is too strong a word. 'Speculation' might be more appropriate.
For some reason, whenever I read a book by an evolutionary psychologist I get the feeling that I've read something like this before in an astrology text. Granted, there are no references to planets or stellar objects that are supposed to explain such things as why the typical human sleep cycle lasts about 90 minutes, but the explanation in terms of how our "ancient ancestors" adapted to their environment seem like the same kind of confirmation bias and just-so stories that astrologers devise, or the kind of stories mythmakers devise to explain the origin of a rock formation called The Old Hag.
I have four problems with these kinds of explanations. One has to do with the slippery expression "ancient ancestors." It seems that this can refer to any imagined group of animals in the human evolutionary line existing at any time from 2,500,000 years ago to about 200,000 years ago when humans began migrating out of Africa. Second, the stories seem to assume human evolution stopped about 200,000 years ago when the African migration began. The stories take it for granted that no meaningful human evolution has taken place since agriculture replaced the hunter-gatherer lifestyle, despite the fact that there is strong evidence that humans continue to evolve. Third, the stories seem to place these ancestors in whatever kind of environment fits with whatever kind of point the author is trying to make about some current human behavior or biological process. The stories often use evidence from modern "stone age" peoples to speculate, but clearly the lifestyles of these folks don't resemble the lifestyles of our pre-human ancestors. Fourth, the arguments often seem circular: some current behavior or physiological process is used to speculate about some Stone Age behavior or adaptation, which is then used to explain the current behavior. For example, women with multiple pregnancies and women on birth control pills have lower ovarian cancer rates. Stone Age women were usually pregnant and had many fewer menstrual periods than modern women (20 vs. 400, according to Meller). This protected them from ovarian cancer. Women today can protect themselves from ovarian cancers by imitating their Stone Age sisters and reducing the number of their menstrual cycles.
Anyway, I find it hard to accept such claims as 'the 90-minute sleep cycle is due to our ancient ancestors having to wake up several times during the night as a survival tactic.' The hypothesis is that without this cycle the danger of being eaten while sleeping would make survival much less probable. But why 90 minutes? Do tigers or leopards attack at regular, 90-minute intervals? Are we supposed to believe that many eons ago, our ancestors woke up at various intervals from every few minutes to every six or seven hours and that the ones most likely to survive and reproduce were those lucky ones who fell into the 90-minute cycle? And that's why our sleep cycle is 90 minutes. It's an interesting story, but I don't know how you'd test it. Anyway, I don't find it very satisfying, but it seems to be the kind of story that pleases evolutionary psychologists.
I'm not against speculation, but I don't like my speculation to be too farfetched. There's a lot of uncertainty regarding what life was like for our Stone Age ancestors, especially the ones who lived before the African migration. It is very unlikely that when human groups moved out of Africa and spread out around the globe that each community always found itself in the same kind of environment and always ate the same kind of diet. It seems fair to assume that humans are quite adaptable when it comes to diet and environment. It seems plausible to me that human evolution has continued throughout our history, that our ancestors found themselves in all kinds of varied environments from profound scarcity to abundance, from environments where they ate little besides meat and tubers, to environments where they ate a good amount of wild grains and plants. No one diet has served all human communities in the past and it is unlikely that one diet would serve us in the present. Our Stone Age ancestors ate whatever was available. Many people on the planet are still in the same situation, which is unfortunate. Many of us in the U.S. and elsewhere today can design our diet to include or exclude just about anything our tummy or head tells us to. Do we really need to speculate about the diet of Stone Age people to determine what ought to be in our diet today? I don't think so, but Meller does. I'd prefer to rely on current scientific knowledge about the effects of the many potential substances I might ingest than on speculation regarding the diet of creatures I probably wouldn't invite to dinner were they alive today.
Meller's primary assumption is that many of humankind's biological and psychological changes that most intimately affect our health today took place between 2.5 million and 1.6 million years ago in what he refers to as the Stone Age: "the million-year-long period when we evolved from little more than speechless, hairy apelike hominids into fully modern humans." From this basis he thinks he can explain such things as why we get the kinds of diseases we get and what kind of diet would be best for us. He believes that living in harmony with our "inborn past" is the key to "optimal health and happiness." He says he uses evolutionary stories to help his patients deal with injuries and illnesses, and that he's seen "dramatic and positive" changes in them. So, it works for him, but whether such an approach has general medical value needs more than personal experience and anecdotes to establish.
the Stone Age diet
Chapter one is all about food. He recommends a low-carb diet not just for those of us who are obese or diabetic. He recommends it for everyone. We should avoid bread, cereal, pasta, potatoes, rice, beans, and other grains. Why? One reason he gives is that none of these items "was on the menu in the Stone Age." I'll bet there are millions, maybe even billions, of people on this planet who would be very happy to have a few of these high-carb items on their plates. Anyway, of all the reasons one might give for leaving these fine foods off the menu, the least appealing to me is that the hairy hominids we've descended from didn't have them. There are better reasons for us fat diabetics to cut down on the carbs. Meller provides the main one: leptin, ghrelin, orexin, cholecystokinin, neuropeptide Y, and aguiti-related peptide "only work when we eat fat and protein." These are the "hormones of satiety...internal chemicals [that] act as switches to shut off our appetite when we have eaten enough." A low-carb diet makes it easier to eat fewer calories without feeling hungry, and eating fewer calories is the only sensible way to lose a significant amount of weight.
Even so, a low-carb diet won't work any better than any other diet in the long term, and most physicians would probably disagree with Meller's advice to get 50% of your calories from meat and fish, 40% from vegetables, and less than 10% from fruits and grains. Why these ratios? Because studies show this is what the Stone Age diet consisted of. Meller advises us to be omnivores, eat a wide variety of foods, and maintain a healthy weight. The only justification for vegetarianism, he thinks, is ethical, but warns vegetarians of their ethical obligation to their children. A purely vegetarian diet may be nutritionally deficient for growing children.
Most MDs would probably advise following the American Cancer Society's recommendations for diet: lots of fruits and vegetables; some whole grains and legumes; a little meat and not much alcohol, along with regular exercise and weight control. Meller thinks exercise is good for feeling good but not for losing or maintaining weight. He also thinks two glasses of wine, beer, or booze is good for you (if you want to live longer). There are billions of people on our planet who would love to follow one of these diets, but they don't have the resources or the foods aren't available to them.
Meller claims that before the advent of agriculture "most foods contained almost no edible carbohydrates, like starch and sugar." Maybe so, but I don't find this to be a compelling reason to avoid edible carbohydrates. There are compelling reasons for limiting carbohydrate intake, however. As Meller notes, sugars come from carbs, not fats and proteins, and sugars feed the bacteria on our teeth and stick to the lining of the capillaries that supply blood to our organs and tissues, which can trigger all kinds of other health problems.
Some doctors might be concerned that following the Stone Age diet would lead to higher cholesterol and more heart disease. Meller says the evidence shows that cholesterol is a much maligned molecule. Most people who have heart attacks have normal cholesterol levels. Without cholesterol, we'd die. Many people have high cholesterol and no heart disease. No study has ever shown that cholesterol causes heart disease. Cholesterol-lowering medications provide "little or no benefit."
In contrast, Dr. Harriet Hall of Science-Based Medicine writes:
• High blood levels of LDL cholesterol are a significant risk factor for cardiovascular disease.
• For primary prevention, lowering high LDL levels in high risk patients is associated with lower morbidity.
• For secondary prevention, lowering high LDL levels is associated with lower mortality.
• Low fat diet is only likely to lower LDL levels slightly (3-6% by one estimate).
• Statins are effective in lowering risk when prescribed selectively for patients at high risk, although the NNT (number needed to treat for one person to benefit) is relatively high.
She admits, however, that "the general public is way too concerned about cholesterol and fat in the diet, too concerned about blood cholesterol levels and not concerned enough about other modifiable risk factors" such as smoking, overeating, and choosing better parents. Just kidding about the last, of course, but if you're looking for sources of why you are the way you are, you could do worse than to consider the genetic hand you've been dealt.
I've been reading Dr. Hall's work for several years and have almost always found her to be a reliable source. I've been reading Dr. Meller's work for only several days and already I have grave doubts about his reliability in speculative matters. I was a bit put off by the fact that I couldn't find appropriate references for some of his more unusual claims in the "Sources and Further Reading" section of his book. For example, he claims that some scientists think a high-carb diet contributes to the development of myopia. I could find no reference to follow to see if these scientists are worth considering, and Meller offers no discussion of the issue.
On the bright side, Meller discourages using vitamin and mineral supplements, including antioxidants, but not because our Stone Age ancestors didn't use them. Most people get enough nutrients in their daily diet, whatever that diet might be. (I assume he's talking about people in countries with abundances like the U.S.).
Also, when it comes to something he approves of, namely vaccinations, he isn't concerned that Stone Age folks didn't have them, and he is quite willing to admit that vaccinations are an improvement. To be fair, he repeatedly notes that he's not advocating a return to the Stone Age.
Readers looking for some medical mythbusting will not be disappointed with this book. Meller debunks the myths that good health requires eight glasses of water a day and no salt, that a high fiber diet protects against colon cancer, that modern life is toxic, that organic foods are more nutritious than conventionally grown foods, that the human body is intelligently designed, that one should do a lot of stretching before exercising, that you can cure diseases with happy thoughts, that exposure to sunlight increases your risk of melanoma, that we need supplements to stimulate our immune system, that aspartame causes cancer, that allergies come and go, that we should avoid anything that has any amount of a harmful substance, that we can't overdose on vitamin pills, that we're in danger because of pesticide or bisphenol A residues in our cells, and that menopausal women who use hormone replacement therapy (HRT) greatly increase their risk of developing breast cancer. Regarding the latter, Meller notes that researchers did find 7 more breast cancers per 10,000 women in the hormone replacement cohort of the Women's Health Initiative (37 vs. 30/10,000 in women not using hormone therapy). In an article published in the November 2009 issue of The American Journal of Medicine, researchers concluded that HRT almost certainly decreases mortality in younger [average age = 55] postmenopausal women. "The total mortality benefit for younger women seen in the randomized trials and observational studies indicates that the reduction in deaths from coronary heart disease, fracture, and colon cancer outweighed the increase in deaths from breast cancer, stroke and pulmonary embolism." [This is contrary to Harriet Hall's claim in her review of Meller's book. update: Dr. Hall informs me that this is not contrary to her claim. "My claim was from the original study of postmenopausal women of all ages, in which there was no overall difference in mortality. This is a different, more recent study of only a younger segment of the postmenopausal population. It does not invalidate the findings of the original study, it simply explains some of its wrinkles. Presumably, if the younger women benefit, some of the older women are harmed so that the overall mortality balances out. This is important and good to know, but it is still true that HRT does not increase mortality overall."]
On the other hand, Meller might be creating a few new myths of his own. Does he really believe that "tuberculosis was in rapid decline, even before antibiotics, largely due to the immune-stimulating effects of sunlight"? According to WHO: someone in the world is newly infected with TB bacilli every second. Overall, one-third of the world's population is currently infected with the TB bacillus. And, the first case of highly drug-resistant TB has been reported in the US.* is true that sunlight stimulates the production of vitamin D, which is essential for a healthy immune system. But sunlight also exposes us to UV radiation, which has a detrimental effect on the immune system. Melanin protects us from these harmful effects but it does not provide complete protection, and we are not created equal when it comes to the amount of melanin we have. The darker the skin, the more melanin. Albinos lack melanin. Like most things that are good for you, sunlight is good in moderation.
He thinks men go bald because evolutionarily speaking bald guys get more chicks. Why? Because baldness signifies youth and virility. Really? I thought baldness signifies youth and the need to be cuddled, which triggers the urge in young women to suckle.
medicine and evolution
It's pretty clear that a knowledge of evolution is useful in understanding diseases like cystic fibrosis and sickle-cell anemia. It's also clear that things like pain, fever, and mucus evolved for a reason. Meller explores these kinds of things where speculation isn't farfetched, but because there are so many other topics he deals with that are fuzzy at best, I question whether there's really much value in having a book devoted to evolutionary medicine. There are many good reasons for not smoking; the fact that Stone Age man didn't smoke isn't one of them, however. And I really don't know what to make of his claim that we can decrease the risk of the most common cancers by 90% if we eat well and don't overeat, don't smoke, expose ourselves to sunlight for vitamin D, and (for women) reduce the number of menstrual periods. If this is true, then billions of dollars and research hours have been wasted on cancer research. That doesn't mean Meller's wrong, but I'll have to do a lot more reading before I'd accept his assessment.
I'll conclude with some comments about Meller's views on how we should treat mental illness.
His overall view seems to be that there was no mental illness in the Stone Age. We call people who behave in certain ways 'mentally ill,' but their kinds of behaviors would have been beneficial to the survival of individuals or Stone Age groups. Maybe so. Meller doesn't mention schizophrenia, but I suppose this disease benefited Stone Age groups by providing them with people who seemed to be in touch with another dimension of reality that might provide the tribe with protection from enemies by magical, ritualistic, behaviors or incantations. Such people could serve as gods or conduits to another dimension. Perhaps schizophrenics were the first shamans.
Meller thinks mental illness exists on the extremes of continua: depression is extreme sadness; mania is extreme gladness; anxiety is extreme fear. He thinks people with ADHD (attention deficit/hyperactivity disorder) were the ones in the Stone Age who were always on the alert and warned the tribe of dangers. Their inability to sit still made them the watchdogs of the tribe. Their hypersensitivity made them the first responders to danger. Without ADHD, says Meller, "the human race would have been someone else's lunch long ago."
Meller recommends cognitive behavioral therapy (CBT) for most mental illness except for the cases where it doesn't work and medication is required. (Not a very useful principle, is it?) He agrees we need to medicate sometimes, but he thinks we medicate in many cases where we don't need to and where we shouldn't. That's probably true, but again, not very useful information. Anyway, what does evolution have to do with this? In Meller's view, CBT is "simply a reformulation of our ancient ability to overcome fear." How he knows that some Stone Age people figured out how to modify their thoughts and behavior, beyond simple common sense that told them to move on to less dangerous, more fruitful places, is something Meller takes for granted. I'm all for CBT, but I think the reason for using it is that it works today, not that it worked for Stone Age folks. Meller doesn't discuss it, but CBT is being used with some success for bipolar disorder and schizophrenia, two of the more severe forms of mental illness.
Finally, what does Dr. Meller have to say about the folk medicine principle that we should feed a cold and starve a fever? He thinks it's brilliant advice, but I don't think Meller or anyone else knows what Stone Age man did when he got infected by some animal he hunted down. Frankly, I don't think any of us really give a damn. Anyway, here's the science, according to Meller: feeding a cold increases the production of interferon, a virus fighter; starving a fever stimulates the production of interleukin 4, a fighter against bacteria that cause fevers. Dr. Chris Smith of The Naked Scientist podcast disagrees with the idea that we should starve a fever. With fewer nutrients we produce fewer memory B cells, which make antibodies that defend us against infections. Reducing food intake reduces energy for our cells, which would mean less energy for mounting an effective immune response to infections.
If I had to give a thumbs up or down to Meller's book, I guess I'd give it one thumb up and two thumbs down.
On the positive side, see Immune system quackery.