New Under the Sun:
Volume 5, Issue 3
As the sun rises earlier each morning and sets later each night, it seems that we have more time during the day to initiate and complete activities. Trees and flowers are blooming. Life seems full of possibilities.
Domesticated Behavior: This month’s news article is not recent, but it is provocative and fits with this month’s focus on evolution and health. As the authors of the article point out, we still do not fully understand why and how agriculture became so widespread and at relatively high speed. Many people probably think, well, it is self-evident. Agriculture was obviously the better way to go. But this is actually far from the case. Populations that adopted agriculture saw a dramatic, long-term decline in their health.
Stature plummeted. It was only in the late 20th century that stature recovered in industrialized nations to pre-agricultural levels. Agriculture brought with it so many problems such as epidemic diseases, reduced life-span, overpopulation, poor sanitation, etc., etc., that it is no wonder that some populations refused to adopt it without force. Given this, the authors decided to see if there were some biological/behavioral reason that would encourage people to forsake a varied, healthy diet for one that had extremely limited nutritional value, relying as it did on grains such wheat for the primary dietary component.
What they discovered is quite surprising. The foods of agriculture (grains and dairy products) produce exorphins (in wheat, etc.) and casomorphins (in milk, etc.). These substances create results similar to opioids in that they activate the reward center of the brain when eaten; they become addictive; and withdrawal symptoms can occur when the individual quits eating them. The reward/pleasure they induce is calmer, more relaxed behavior. Since these agricultural products are so recent in human evolution, it is unlikely that we are adapted to ingest them on a regular basis. These are the same foods that cause allergic reactions and/or intolerance in many individuals and yet, curiously, these are also foods that these same individuals crave and from which they show withdrawal symptoms when not allowed to eat them. As the authors state, “There is no possibility that craving these foods has anything to do with the popular notion of the body telling the brain what it needs for nutritional purposes. These foods were not significant in the human diet before agriculture, and large quantities of them cannot be necessary for nutrition.”
The authors’ hypothesis is that ingestion of agricultural products calmed and sedated individuals sufficiently to allow them to congregate in large groups without excessive disruptive behavior. This provided the population density needed to create urban centers and, eventually, the world we now have. “Cereals have important qualities that differentiate them from most other drugs. They are a food source as well as a drug, and can be stored and transported easily. They are ingested in frequent small doses (not occasional large ones), and do not impede work performance in most people. A desire for the drug, even cravings or withdrawal, can be confused with hunger. These features make cereals the ideal facilitator of civilisation (and may also have contributed to the long delay in recognising their pharmacological properties).”
Greg Wadleya and Angus Martinb The origins of agriculture – a biological perspective and a new hypothesis. Journal of the Australasian College of Nutritional & Environmental Medicine, Vol. 19, No. 1, April 2000, pages 3-12.
Comment: As the authors point out, more research is needed to decide whether the evidence supports their hypothesis or not. But it is quite intriguing. As regular readers know, the AnthroHealth diet does not include grains and dairy products for the reason that these would not have been eaten by our pre-agricultural ancestors and would not have been part of the diet for which our bodies and health are adapted. For those who found that reasoning insufficient to cease consumption of those foods, perhaps this new information might help. Readers can eliminate grains and dairy from their diets for a week or so and see if they suffer from mood swings and irritability. If cravings ensue, perhaps that might be sufficient reason to replace grains and dairy with more tree nuts, fruits, fish and shellfish, etc.
Book Review: Paul Ewald has devoted his career to providing an evolutionary basis to modern medicine. Without such a basis, medicine tends to be a disparate collection of methodologies rather than a coherent entity. Modern medicine is in much that same place as natural history was in the mid-19th century prior to Darwin: a disparate collection of facts about a variety of plants and animals lacking the coherent basis provided by Darwin with his explication of natural selection. With the explanatory basis of natural selection, natural history became biology. Modern medicine must recognize that it, too, requires the explanatory basis of natural selection if it is to be truly effective in the 21st century.
Plague Time: How Stealth Infections Cause Cancers, Heart Disease, and Other Deadly Ailments is Ewald’s most recent effort (ca. 2000) to alert the public and medical professionals to the potential long-term negative impacts of current medical practices. Ewald’s major thesis is that many chronic diseases have an underlying infectious causation. In most cases, he views the infection as one factor among many, including genetic and environmental, not as the sole cause of a particular disease.
Part I of the book explains evolutionary medicine and why this approach is necessary for disease prevention. In support of this book’s thesis, Ewald cites the cases of peptic ulcer and cervical cancer, both of which have been found to have infectious causation: ulcers by H. pylori and cervical cancer by human papillomavirus (HPV). In addition, research has shown that pathogens play a role in heart disease and liver cancer. It is not much of a stretch to look for pathogenic causes of other chronic health problems.
For presumed genetic causes of disease, genetics researchers are searching for ways to successfully modify genes. So far, this has been with little success and some unforeseen deaths. We really have no idea what will happen downstream when we attempt to modify the functioning of a gene. This is also true of the immune system: we really do not know what will happen to such a complex system when we attempt to modify it. Ewald views vaccines and antibiotics as simple “tweaks” to a complex system; essentially no more than sending out a “mugshot” of the pathogen to be captured. As Ewald states, “The immune system, like the brain, was engineered by natural selection to be a self-controlling unit. It therefore does not have controls that allow an outside user to turn one attribute at a time up or down. If we increased a chemical messenger to try to improve immune function, we would probably cause many unforeseen effects as the immediate response affected other parts of the immunological web.” [p. 65] If we cannot safely modify the immune system, the best course of action is to limit the pathogen load the immune system must handle.
In Part II, Ewald discusses a variety of pathogens and their evident role in some chronic diseases and possible role in others. For instance, Ewald notes that a virus is known to cause mammary tumors in mice. In a sample of human breast cancer tumors, this same virus was found in over one-third of the tumors. This indicates an area requiring more research. It would be especially informative to determine if the one-third of patients who had the virus in their tumors were in closer association with mice than were the other patients since the house mouse is the primary host of the virus. Another example Ewald cites concerns atherosclerosis. Non-infectious risk factors account for only about 50% of cases. The other 50% develop atherosclerosis despite lacking problematic risk factor indicators. Ewald proposes that the missing factor is infection with C. pneumoniae, and that this pathogen is involved in other diseases such as lung cancer. Ewald also notes that clusters of cancer cases may be more the result of infection than of a carcinogenic chemical. There are many other topics Ewald discusses, but this can be only a brief review. For further information on this fascinating topic of infectious causation of chronic disease, you will need to read this book.
In Part III, methods of prevention are detailed. One of the most important points that Ewald makes several times is that pathogens do not necessarily evolve to a more benign form. Whether they become more benign depends in large measure on their mode of transmission and any health or sanitation measures in effect in a population. Vector-borne diseases, such as malaria, may need to become benign in the mosquito vector, but there is no selection pressure to become benign in diseased humans, as long as mosquitoes can access the diseased. The sicker the human, the easier this is. We could try to spray the mosquitoes out of existence, but it appears that they are developing resistance to even the most dangerous pesticides. Then what? Ewald’s solution is low tech: use screening at windows and doors. This prevents access by mosquitoes to the really sick individuals which means that the deadlier forms of malaria will be less successful in those regions where buildings have screening and will replaced by the milder forms. Similarly, water-borne pathogens do especially well when humans are very ill. It is only with improved sanitation, which limits transmission of the pathogen, that milder forms of the pathogens become more successful.
Also under the heading of prevention, Ewald discusses the possible uses of designer pathogens by terrorists and concludes that, “[u]nless terrorists can outclass the best minds in epidemiology, we can safely assume that the use of biological weapons would be a bad move by any terrorist looking to cause a particular severity of infectious outbreak… Infectious agents do not restrict themselves to ethnic or national boundaries.” [p. 186] Since this book was published in 2000, Ewald’s discussion seems rather prescient in the post 9/11 world. It may also explain why we have not [yet?] seen a biological terror attack.
The best way to encourage benign evolution of a pathogen is to prevent its spread. And the best way to prevent spreading pathogens is to stay put (in a screened, sanitary place) until one is well again. Although this is logical, it is also extremely difficult to implement in our current work world climate where staying home when ill is often seen as a sign of weakness or a copout. In addition, many workers receive few or even no sick days. The business world actually unknowingly conspires with the pathogens to increase their spread. The medical and pharmaceutical fields also inadvertently increase pathogen spread by delaying recovery through suppression of symptoms. “The advertisements do not actually say, ‘Feel better fast so that you can spread disease within your community,’ but that is certainly their short-range effect. Their long-range effect is just as disturbing. The advertisements encourage the spread of nasty variants, whereas from an evolutionary point of view we need to do just the opposite. If people stayed home when they felt the least bit sick, the pathogens that would be left to circulate in the community would be those that rarely, if ever, made a person feel the least bit sick.” [p. 210-211]
Other preventative measures include vaccines and antibiotics. Unfortunately, from the perspective of evolution, Ewald notes that we have been using both in unwise ways. Vaccines should be selectively constructed to provoke immune response to only the most severe variants of a pathogen. The same is true of antibiotics: they should be used in a specifically targeted manner, not in a broad-spectrum, scattershot manner. The reason for this is that the variants that survive the natural selection process will then be milder forms. If we eliminate mild strains, we could be giving more harmful strains an unexpected boost.
Ewald has put together a strong, well-reasoned argument for infections having a role to play in the onset of chronic disease. He also provides common-sense suggestions for limiting the virulence and spread of pathogens. And while I agree that the immune system is extremely complex, he ignores a factor which actually could strengthen it without causing harm. That factor, yes, is optimizing vitamin D levels. Many of the chronic diseases he mentions as having infectious causation such as multiple sclerosis, heart disease, and breast, colon, and prostate cancers, are also those associated with sub-optimal vitamin D levels. Vitamin D receptors are found on tissues of the immune system. It therefore would follow that suboptimal levels of vitamin D would lower the effectiveness of the immune system which may result in the incursion of pathogens that could ultimately lead to chronic disease.
Plague Time is a well-written and intriguing introduction to the field of evolutionary medicine. It is a field that needs to be integrated into medical school curricula if we are to effectively practice preventive medicine. “Prepared minds need to recognize that evolutionary processes are intimately involved in human disease. To deny this assertion is to deny the whole of biology. But integrating evolution into medicine requires a deep understating of natural selection.” [p. 237] If we are to have better medicine, it appears that high school and college biology courses will need to do a better job of teaching evolution and natural selection. Pathogens are rapidly evolving past out medical defenses. If we do not understand how this occurs and how to prevent it, we may find modern health reverting to pre-modern standards.
AnthroHealth Tip of the Month: The next time you feel ill, if it is at all possible, plan to stay home until you feel better. In addition, if you have a cold, you should avoid taking cold medication. You will have the impression that you are better, but you will be delaying your recovery. The best thing to do to give your immune system a fighting chance is to follow the age-old advice: stay in bed, sleep, and drink plenty of fluids.
© 2001-2009 Kathleen E. Fuller, PhD. All rights reserved.