Homeostasis is really about balance, and in this case, energy balance. We are predisposed to maintain this homeostasis by taking advantage of surplus energy and storing it as fat. And while this trait has served our species for 2 million years, we no longer live in a feast or famine environment, and those conditions of the seasonal rarity of food calories no longer exist. Most of us have very easy access to high caloric foods, free of the environmental stress that our hunter-gatherer ancestors were forced to contend with daily. Today, we are not balancing our intake/expenditure well.
Those same ancestors who benefited significantly from this fat storage of excess energy (a significant evolutionary advantage) are growing obese and suffering from dozens of associated diseases. In today’s readily available high caloric foods, stored just as efficiently, yet we do not contend with the same environmental stressors. Finding sufficient food even a few thousand years ago was often tricky, and required significant work.
To find 1500 calories, our hunter-gatherer ancestors would have walked or run an average of 6 to 10 miles. Although we possess the same biology and physiology, we can now consume 1500 calories at breakfast, all while sitting in a chair. In other words, this evolutionary trait that served our ancestors so well has become a significant liability. The issue is energy balance. We take in far, far more than any hunter-gatherer ancestor, at the same time expending almost nothing.
Our ancestors spent significant energy and time finding sufficient sources of protein and healthy fats, and early in our history our ancestors identified one excellent source of dense calorie food. But obtaining it required endurance, focus, and stamina. A great deal of stamina.
Humans, unlike most other predatory mammals, lacked claws, fangs, and speed. The fastest human could not keep pace with deer or antelope; however, by using teamwork and endurance, our ancestors could run down prey animals as they became exhausted. Even smaller prey animals can become dangerous when cornered; however, once exhausted they were much safer to approach and dispatch. Persistent hunting was a technique that allowed hunter-gatherers, through a combination of running and walking, to pursue prey species. We can see the same hunting strategies in pack animals like wolves, African wild dogs, and some species of hyenas. Humans, with our evolved ability for endurance, combined with sparse body hair and the ability to sweat while running, places us at a significant advantage over most mammal species that must pant to cool down, requiring them to slow or stop moving.
Medical scientists and sociologists see this strategy at use still today among groups of hunter-gatherers in the Kalahari Desert and groups in northwestern Mexico. In his book Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen, author Christopher McDougal explains that throughout human history we have had one advantage over other predatory mammals: we can run long distances on hot days. It is not uncommon to watch nature programs that show hunter-gatherers walking in small groups while lions and other carnivores watch them from the shade. This is why our ancestors learned to hunt during the hottest part of the day: little competition from other predators, relative safety due to the heat of the day, and prey animals also susceptible to the heat. Many large mammals sweat through expiration, so prey species like deer, elk, or even mammoth, have a choice to make; keep running while taking shallow breaths and eventually overheat, or stop to breathe and rest. Humans tracking the animals would soon overtake them, and the animal would have to run again. Eventually, heatstroke overcomes the animal, and it is forced to stop.
Louis Liebenberg, writing in Current Anthropology, identifies the reason that those groups of humans that still practice endurance hunting are among the healthiest humans on the planet. Human bodies, thanks to biological evolution, are predisposed to maintain homeostasis, which is particularly important to remember when storing fat against future food shortages, especially in modern nations where food shortages do not exist. Nutritional deficiencies are a different matter. Because food was difficult at the best of times to harvest in any quantity for our ancestors, our physiology and biochemistry evolved to use every gram of fat and protein, storing any excess for future use. The problem is that in the modern world, there are no periods of scarcity, and unlike our ancestors, we do not have to put in physical work to obtain it, leading to a significant imbalance of intake and expenditure. This imbalance has been at least partially explained by the Thrifty Gene Hypothesis.
According to this theory, for the vast majority of our history, humans lived under feast or famine conditions, and over thousands of years, we developed traits that allowed us to use the available food calories and store any surplus efficiently. Hunter-gatherers who lived under this environmental stress naturally benefited, as the next meal was never guaranteed. When food was plentiful, which was rare, humans consumed as much as possible and the excess calories were stored as fat. One can easily see how this would have significantly benefited our ancestors, but as modern humans living a mostly sedentary lifestyle with easy access to calorie-dense foods, this same genetic predisposition is very detrimental to our health.
Harvard University evolutionary biologist Dr. Daniel Lieberman states that while our ancestors walked several miles to harvest their daily calories, many modern humans consume huge amounts for breakfast while sitting in a chair. In a world of cubicles and office work, fewer calories are burned in a day and combined with significantly higher amounts of calories consumed, the result is predictable. Perhaps most adults living in modern societies have diets that are considerably lacking nutritional value, leading to a physiological craving for fat and sodium. When combined with a sedentary lifestyle, we consume far more calories then we burn. Meanwhile, those thrifty genes that enabled our ancestors to survive food scarcity now work against us. Our body still stores calories that we do not burn as fat, and we’re not burning nearly enough to counter what we consume; the result is an imbalance of energy, which can result in obesity, and may lead to or worsen inflammatory conditions including cardiovascular disease, liver dysfunction, hypertension, and insulin resistance. When two or more of these inflammatory conditions occur along with Type-2 Diabetes (Diabetes mellitus), the resulting diagnosis is Metabolic Syndrome.
In my area of expertise, infectious disease, modern science and medicine have been very successful in combating morbidity and mortality from once deadly infections. Since the inception of the first vaccines (vaccine comes from the word Vacca, Latin for cow), infant mortality has dropped drastically in developed nations. These chronic conditions, even those that once struck middle-aged and older, are now being seen in young adults and even children. Diabetes, heart disease, asthma, lupus, and many other autoimmune diseases are conditions of excessive inflammation. When examined through the lens of the inflammatory process, substances such as sugar, corn syrup, and several other overly processed food products are cytotoxic, in other words, they damage or destroy living cells. In the 1970s, a cartoon public service announcement featured a yellow cartoon man in a top hat, whose name was apparently “Timer.” The ad would play in the middle of afternoon cartoons, and the message was always the same: you are what you eat. This was true then, and it is undoubtedly true today. The Western diet is cheap to produce, cheap to purchase and is filled with refined carbohydrates and simple starches. When the flora of the gut digests these food-like products, the bacteria release endotoxins that trigger inflammatory responses, including those that have been associated with metabolic syndrome, Type-2 diabetes, and obesity.
Other conditions, many long associated with the aging process, can be better explained by the mismatch between ancient physiology and modern western culture.
Osteoporosis is a disorder that has become strongly associated with a sedentary lifestyle. When archaeologists compare the bones from hunter-gatherer ancestors, even those of advanced aged and female individuals, they find an almost total absence of osteoporosis. In modern humans, at least those from industrialized societies, many people (especially women) are susceptible to the loss of bone density during the aging process. Paleobiologists believe that this increase is strongly associated with a sedentary lifestyle and that bones that are not stressed mechanically (walking, carrying children, etc.) will lose bone density due to a lack of physical activity. Not only do archaeologists see a higher bone mass in hunter-gatherers, but an almost universal absence of osteoporosis, despite some individuals having experienced fractures and other injuries early in life.
A sedentary lifestyle, particularly among industrialized societies, create a mismatch well beyond the biological and physiological and can include the neurological and behavioral as well. In hunter-gatherer societies, where physical stress and heightened experiences (the thrill of the hunt) generated a sense of pleasure, this release of dopamine helped ensure the survival of the group by fostering a desire to hunt. Today, the deer hunt is a rite of passage for many North American males who, having experienced the heightened arousal necessary for a hunt, experience a desire to repeat the experience, leading to greater hunting success and as a result, more food. Today, finding that exhilarating experience is more difficult, often requiring us to replicate risky behaviors to experience the same biochemical rush as our ancestors did during their hunt for food. Many argue that the addictive behavior of youth today stands as a substitution for tracking and hunting that our hunter-gatherer ancestors were required to learn as children.
The neurochemical response to risk and chance that flooded the brains of our ancestors on the hunt are seen today in pathological gambling and, among youth, risk-taking behavior. And while embracing novel experiences was of benefit to our ancestors (looking for food in new places, trying new experiences to hunt animals), the desire to try something new and exciting has manifested itself in the modern world of online poker, casinos, and lottery tickets. If you ask a gambler, he or she might tell you the higher the risk, the greater the reward. For our ancestors facing down dangerous prey animals, this was their reality as well. And if we cannot as modern humans satisfy our need for risk and reward through physical activity, we may well find chemical methods to satiate this ancient drive.
These three parts of this article have explained why chronic diseases have escalated in the west, including those illnesses starting to impact children. But it’s not all bad news. You can catch up and reverse these conditions if you are willing to make significant changes in your lifestyle and eating habits.
Significant research has associated a significant risk reduction from some forms of cancer, heart disease, and metabolic disorders with an increase in exercise and removing sugar and other processed foods from your diet. If osteoporosis is a concern, more exercise is beneficial mainly in middle to late childhood and early adulthood. Allergies and autoimmune conditions may be the result of an aseptic environment, according to many immune disease researchers. Let children play in nature, and consider probiotic foods like French style yogurt without added sugar or corn syrup. To avoid myopia, spend more time outdoors in nature, rather than focusing on television, handheld game devices, or cell phones. Research indicates that those who exercise more and sit less experience far less lower back pain. To feel better, get at least eight hours of quality sleep each night. Humans did not evolve to function on five hours of sleep, and several studies indicate that rest allows the brain to rid itself of toxins and to repair networks. Insufficient sleep has been shown to be strongly associated with attention deficit issues, depression, obesity, and cardiovascular disease. Finally, read labels and educate yourself, if not for your health, for your children’s.