Human evolutionary history has unfolded over millions of years and has transformed us from one generation to the next to its current state. In fact, the process of evolution continues to occur today and humans will be different in many aspects generations from now. If you look at human beings through the lens of evolution, it should be of no surprise we are the way we are. As the geneticist Theodosius Dobhanzky wrote, “nothing in biology makes sense except in the light of evolution.” For millions of years, our environment has shaped our adaptations and natural selection has optimized the fitness of its individual members within an environment. However, due to two technological transformations over the last 10,000 years –the agricultural and industrial revolutions – we have started to shape our environment on an unprecedented scale.
These two technological transformations have radically altered every facet of our environment ranging from the climate to our activity levels and nutritional intake. Moreover, the speed of changes especially since the industrial revolution is leading to pathological consequences because of the constraint or capacity to adapt. The agricultural revolution has enabled a more efficient method to produce more food for less work. This in turn allowed individuals “free time” to pursue philosophical and scientific pursuits. This process is continuing at a dizzying speed but came to an inflection point with the industrial revolution of the late 19th century. The industrial revolution was a combination of technological, economic, scientific, and social transformations that has altered the face of the planet in less than ten generations (blink of an eye in standards of evolutionary time). However, this advancement has not come without a cost to our health. We have traded our decreased mortality for increased morbidity and disability. We have devised or adopted a growing list of cultural practices borne from the industrial revolution that have had conflicting effects on our body. This mismatch between the environment and our 200,000 year old biology is compromising the health of large segments of the population and leading to our chronic disease crisis. If you look at our current chronic disease burden within this evolutionary mismatch framework, it is no surprise we are facing the worldwide chronic disease crisis. We are unable to maintain homeostasis due to the scale and speed of environmental changes.
One mismatch that is at the core of our dysfunction is the current energy imbalance. Pre-agriculture, the amount of energy that was acquired was only marginally greater than the energy that was needed to grow, maintain basal metabolic rate, and reproduce. Historically, we have literally lived “hand to mouth,” and subsequently, millions of years of evolution has selected for ancestors who desired energy-rich food with efficient and highly effective conservation mechanisms. However, nothing in human history has changed human energetics more than the agricultural and industrial revolutions. In Western societies, we are easily able to manufacture and consume energy dense nutrients on a massive scale with minimal work and cost. To compound this energy imbalance we are expending far less energy than our ancestors. On average, hunter-gatherers walked approximately 5 to 9 miles every day. In contrast, a typical American walks a third of a mile per day while commuting an average of 32 miles by car. Moreover, whereas we historically consumed nutrients derived from fiber rich carbohydrates, organ meats, and muscle from grass fed animal, we now derive the majority of calories from refined (fiber free) starches, polyunsaturated oils, and the muscle from corn fed animals. We have substituted food quality and diversity for quantity. This energy imbalance combined with a homogenous, micronutrient deficient, and fiber less diet is a significant cause of the epidemic of chronic diseases stemming from metabolic syndrome and obesity. Studies that have looked at communities that have retained some of their ancestral cultures and minimized these mismatches, rarely if ever stricken by metabolic syndrome, coronary artery disease, asthma, breast cancer, or osteoporosis.
These diseases are evolutionary mismatches because they are aggravated by modern lifestyles that are not in sync with our body’s biology. I am not suggesting that we eschew modernity and go back to living as hunter-gatherers. However, we as individuals must always be aware that our default evolutionary setting is energy conservation, and furthermore, our current cultural paradigm facilitates energy accumulation. Consequently, we must always be looking at this energy balance equation and monitor (admittedly coarse) metrics such as steps, weight, BMI, and body fat percentage. Additionally, we must always be aware of the traps put forth by the food industry and learn to thoroughly weed through the confusing data printed on nutritional labels. As medical providers, until we can convert genomic data into knowledge, we must take into account every patient’s evolutionary origin and how that interacts with their current environmental milieu in order to truly ascertain their complete health status.
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