The obstinate refusal of certain religious adepts to accept the fact that humans are capable of evolving, like their animal counterparts, is the fundamental cause of the sometimes violent discord between believers and non-believers. It is also the driving force behind religious fundamentalism which, for some individuals, transposes into terrorism. The sooner all religions accept the fact that Man is not a divine creation, but the product of an evolutionary process, the greater the chance that all religious communities and non-believers can peacefully accept each other and live together in harmony. Evolution is hard to believe because it is hard to visualise. New species don’t suddenly appear, but are the product of an extremely slow process over time. Evolution is an ongoing process and is driven by the forces of natural selection, as described by Charles Darwin. Only animal species that have adapted to their environment survive. Man is no exception, and has successfully adapted to his environment. However, with the introduction of agriculture and the technological advances since the industrial revolution, man’s nutritional environment has changed at such a rapid pace, that the human body has not had the time and opportunity to adapt. This lack of adaptation is underscored by the extremely high prevalence of present-day “life style” diseases such as cardiovascular disease, obesity and diabetes. You could argue that the victims of these diseases have succumbed to the unforgiving forces of natural selection. For the rest of us, it’s high time to change our dietary habits so that we can “return” to our evolutionary past, and not “out-run” our adaptive capability.
If bacteria can evolve, why can’t we?
I’m not a biologist, but I work everyday in one of the most complex ecosystems known to man, the oral cavity. So it’s safe to say that I know a thing or two about bacteria. I have also spent years following the latest research in oral microbiology and immunology for which I developed a passion. My passion was such that I obtained a PhD in the late 90’s, and have still got ongoing subscriptions to several journals. All this to say that I may not know the “ins and outs” of the Holy Bible, but I am quite capable of “defending” biology and, in particular, bacteria. If you want to convince the creationists that there is no such thing as an “intelligent designer”, all you have to do is present them with a textbook of bacteriology. Bacteria, you see, are the living proof that evolution has always been and will always be.
I’m not going to go into any horrendous detail, but I would like to share with you results from 2 fields of research that will underline the fact that evolution is an ongoing process, even for us. Like it or not, from an evolutionary standpoint, you’re not the same “type” of human being as your ancestors five generations ago were. It’s that close. The first set of results concerns the changes in our oral flora, i.e. the bacteria that reside in our mouths. The second field of investigation concerns the rapid changes in our dietary environment, i.e. what we eat, and how it has contributed to the dramatic increase in incidence of the “life style diseases”, due to our inability to adapt due to sheer lack of time.
Bacterial evolution is a mouth-full
The oral cavity is inhabited by over 700 different bacterial species. Most of them live in complete harmony with their host (i.e. you and me). From time to time, however, things get a little out of hand, and the equilibrium between us and our guests is disturbed. This can lead to diseases such as dental caries and gum disease, which people like me are supposed to fix.
If you follow the reasoning of creationists, you would tend to think that God created us in the beginning, end of story. Thus, there should be no biological differences at any level between Adam and Eve and ourselves. Well, creationists are in for a disappointment, because nothing could be further from the truth. Unless, of course, you think that the “intelligent designer” is at work ad infinitum, in which case the argument is already closed.
By analysing calcified dental plaque samples (dental plaque being the “gunge” on your teeth if you don’t brush), Christina Adler and her colleagues from the University of Sidney, showed significant differences in the oral microbiota corresponding to dietary shifts that occurred during the Neolithic and industrial revolutions. The Neolithic age ranges approximately from the beginning to 10,000 years before the present. It is during this time that farming techniques were introduced. The dietary shifts that occurred comprised the incorporation of a carbohydrate enriched farming diet. The second key point affecting people’s mouths, was the industrial revolution which got going at around the middle of the 19th century, and was characterised by the incorporation of industrialised flour and sugar in our diets. The investigators studied 34 early European skeletons by using DNA analysing techniques that could identify calcified oral bacteria. Their data revealed a shift in the oral microbial community from one of health in the hunter-gatherers to one of gum disease in the farmers. Interestingly, stability ensued until the industrial revolution caused a second great change in human diet with the introduction of refined sugars, causing a dominance of cariogenic bacteria (bacteria causing tooth decay). The authors also demonstrated a significant decline in the overall oral microbial diversity of the oral cavity in modern Europeans compared to pre-industrial Neolithic groups, which could make it more susceptible to disruption related to dietary imbalances or the appearance of harmful bacteria.
All in all then, the extremely complex oral microbiota seems to have evolved with time. This evolution concerns not only the bacterial community as a whole, making it more or less pathogenic, but also targets individual bacterial species, with the appearance of new species and the elimination of old ones. Added to this, not only can potentially harmful bacteria colonise the mouth from the outside, but bacteria who are internal “residents” can also turn nasty, depending on the oral environment. But that’s another story. This is surely evolution at its very best, but creationists could argue that bacteria have nothing to do with us as humans, and that, in any case, God “designed” every bacterial species known to man. However, commensal bacterial cells (the bacteria that normally inhabit our bodies) outnumber by far the total number of human cells. It could even be argued that we, as humans, are more defined by the bacterial cells present on and in our bodies than by anything else.
Diet and the “Life-style” diseases: You are what you eat
I have already alluded to the 2 key events that have influenced our dietary intake. The second event (the industrial revolution) has occurred at such a pace, that the human body has, literally, not had enough time to adapt to its new nutritional environment. It is estimated that in the United States, more than 70% of the energy content in an average diet comes from foodstuffs that did not exist before the industrial revolution. In other words, over a period of less than 200 years, which is insignificant in evolutionary terms, the source of energy obtained from our diet has completely changed.
In an extended review of the potential harmful effects of such a radical and swift change in our dietary habits, Begoña Ruiz-Núñeza from the University of Groningen in the Netherlands, describes the role of our modern diets in the maintenance of a constant low-grade inflammatory status, which, in certain individuals, destabilise the age-old link between the immune and metabolic systems. It is as if our modern diet were “fighting” against our more ancient genome which has had no chance to adapt to the new conditions.
With the advent of the agricultural and industrial revolutions, we have introduced numerous false inflammatory triggers in our lifestyle, driving us to a state of chronic systemic low grade inflammation that eventually leads to typically Western diseases via an evolutionary conserved interaction between our immune system and metabolism. The underlying triggers are an abnormal dietary composition and microbial flora, insufficient physical activity and sleep, chronic stress and environmental pollution. B. Ruiz-Núñeza et al. 2013
One of the consequences resulting from the imbalance is the onset of what is known as the “metabolic syndrome”. This syndrome is, in fact, a cluster of conditions comprising an increased blood pressure, high blood sugar, excess body fat around the waist, and elevated cholesterol or triglyceride levels. When these anomalies occur together, the risk of contracting heart disease, a stroke and diabetes is significantly elevated. One of the causes of the metabolic syndrome is the body’s increased insulin resistance. Insulin is a hormone that decreases circulating blood glucose levels, and promotes glucose absorption by cells and tissues that need it as an energy source.
The brainier I get, the more sugar I eat
The human brain requires a constant amount of glucose as energy source. If the sugar intake is reduced, other tissues will be “sacrificed” in order to maintain the brain glucose consumption. From an evolutionary point of view, the Homo sapiens brain has more than tripled in size compared to that of our first ancestors. This dramatic increase in size was made possible by the presence of a land-water ecosystem in Africa some 2.5 million years ago, which provided high quality and highly digestible food. This allowed our ancestors’ digestive system to be “sacrificed” and “kept to a minimum”, for the body to be able to accommodate the energy requirements of an enlarged brain.
The importance of the human brain goes without saying, and its nutritional requirements remains constant, no matter what the circumstances. In times of low glucose availability, the brain takes precedence over everything else, and other tissues have to adapt. You can well imagine that if there is a constant ongoing low-grade inflammation, the immune system will also “demand” high glucose consumption to maintain its life-saving activation. In this way, since the brain’s glucose consumption remains unchanged, other tissues will be greatly affected by the low concentration of circulating glucose by insulin. In order to “save” glucose consumption, these tissues will appear to be “insulin resistant” and be unresponsive to the effects of insulin for their glucose requirements. During inflammation, the circulating glucose levels will substantially fall due to preferential glucose uptake by brain tissue and the immune system. In short, despite the presence of circulating insulin, tissues will not be affected by it as they normally are, having been “switched off”, and are forced to use other sources for their energy requirements. As compensation for ever decreasing blood sugar levels, more insulin is released in an attempt to prevent the blood glucose levels from falling too low. Insulin, however, has many functions, and not all are blocked by insulin resistance. The high levels of circulating insulin are responsible for practically all the metabolic syndrome’s clinical manifestations. In fat cells, for example, it causes reduced uptake of lipids which then remain in the blood stream and can be deposited on the blood vessel walls, causing a narrowing and/or obstruction of these vessels (atherosclerosis).
But what is the relationship between diet and the systemic low-grade inflammation? Studies have shown increased inflammation in subjects whose diets are high in refined starches, sugar, saturated and trans fats. Diets rich in omega-3, natural antioxidants, phytochemicals and micronutrients commonly found in fruits and vegetables have, on the other hand, been shown to decrease the level of low-grade inflammation. It is thus becoming clearer that dietary components have the ability to modulate the immune system and have a direct positive or negative affect on inflammation. In 2009, Philip Cavicchia and his team at the University of South Carolina, published a paper in the Journal of Nutrition describing a new tool, based on a pro-inflammatory biomarker, that could assess the beneficial or detrimental effects of an individual’s diet on the appearance of chronic low-grade inflammation. The use of proinflammatory biomarkers could help healthcare professionals in advising adherence to healthy diet patterns, such as Mediterranean diet, that reduce the level of chronic low-grade inflammation.
For B. Ruiz-Núñeza, we should “take a step back” in evolutionary terms, and resemble more our pre-industrial revolution ancestors in our dietary habits.
Resolution of the conflict between environment and our ancient genome might be the only effective manner for “healthy aging,” and to achieve this we might have to return to the lifestyle of the Paleolithic era as translated to the 21st century culture. B. Ruiz-Núñeza et al. 2013
It is clear that our dietary habits and sedentary life-styles can cause major problems to our finely tuned metabolism. It is also probable that our genome has not been able to adapt our bodies to the excessively rapid change in our nutritive environment. From an evolutionary point of view, to preserve our future, it’s maybe advisable to revisit our past. We could, of course, seek advice from our “intelligent designer”.