Does our lifestyle fit our genes?
Humans evolved in a vastly different environment to the one we are living in now. We like to think of ourselves as somehow exempt from the rules that govern evolutionary biology but in fact, we’re not. We are an organism, just like any other organism, and we are subject to the same evolutionary principles. Our genes and our biology adapted over tens of thousands of generations to allow us to survive and thrive in a specific environment. But if that environment changes faster than our genes can adapt, a mismatch occurs.
Before farms and factories existed, humans lived most of our history as hunter-gatherers. The environment has changed dramatically in the last 10,000 years. Our first huge shift took us from hunter-gatherers to farmers, and then we took another massive leap into the Industrial Revolution. Even in the last fifty to one hundred years, our world has changed in profound ways.
Our genes have not been able to fully adjust to these changes. Genes typically take hundreds or thousands of years to change. Approximately 10% of our genes have shown signs of adapting since the beginning of agriculture, while 90% are the same as they were during the hunter-gatherer period, which represents most of human evolution. The result is a discrepancy between our ancestral genes and the modern environment, which has spurred the chronic disease epidemic.
In Chris Kresser’s book Unconventional Medicine, he demonstrates the speed that our environment has changed by comparing the timeline of human history to a 100m football pitch. A walk across most of that field - 99.5m - represents the amount of time we lived as hunter gatherers. The last half metre represents the time since agriculture was developed. The industrial revolution came along only in the last 20cm. We think the way we live now is normal because it is all we know. Yet it is not normal. It is far outside the norm of human evolution and history.
So, what do we do? We can’t avoid our modern environment altogether. But we can better align our diet, lifestyle and environmental exposures with our genes and biology. It is useful to examine the past for ideas that will help us work out what might be helpful today.
Diet
For most of our evolution, humans ate primarily meat and fish, wild fruits and vegetables, nuts and seeds, and some starchy plants and tubers. Nobody ate processed food. There was no refined sugar, no refined flour, and no vegetable oils. The only food available was nutrient-dense and whole. Preparation was minimal.
Today: our favourite foods are fish & chips, chicken nuggets, pizza, pasta, bread, sugary canned drinks. What a profound difference. We went from a diet that was naturally anti-inflammatory, high in nutrients, and low in calories, to one that is pro-inflammatory, low in nutrients and high in calories.
Little influences our health more than the foods we eat. The modern diet is a prescription for obesity, metabolic problems and all kinds of other chronic diseases.
In the last few years, there have been a growing number of health experts and researchers advocating eating like our ancestors in order to address the growing health concerns of our modern society. How that is defined exactly is up to each advocate, but they all seem to agree that modern foods like refined sugar, refined grains, vegetable oils, food chemicals and processed foods are out. Some also exclude all grains and all legumes (beans). In addition to excluding these modern foods, there is emphasis on adding in high quality animal foods that were available to our ancestors: pasture-raised meats, wild caught fish, as well as making use of the ‘odd bits’ like bones and organ meats.
Through this way of eating, a growing number of people have found a path to better health and vitality, whether it be better sleep, weight loss, improved digestion, mood, or increased energy. Some of the most compelling stories coming out of this movement are the reports of those who suffered for years with chronic health issues that have now been resolved. When the body is given whole, natural foods, free from processing, chemicals, and toxins, it enables the natural processes we all have within us to detoxify and heal.
Light, Sleep and Circadian Rhythm
Until roughly 100 years ago, humans lived in sync with the natural rhythms of light and dark. When the sun went down it was dark and when the sun came up it was light. People generally got at least seven to eight hours of sleep a night.
Today about a third of people in the industrialised world get fewer than six hours sleep up from just 2% in 1960 (Knutson et al. 2010). One reason for this is that, since about 100 years ago, people are exposed to bright, artificial light at night when their bodies are naturally programmed to sleep. This has been a huge advantage from a cultural perspective but has had a negative effect on our health. We take advantage of the expanded day to fit in more activities but doing so disrupts our circadian rhythm. Every cell in our body is regulated by the natural light-dark cycle. When we change that cycle, our bodies suffer.
Other more recent changes, such as working inside in an office during the day, working night shifts, travelling across time zones have also profoundly affected our exposure to light. This has led to several unanticipated and undesirable impacts on our health. Our genes are hard-wired for the twenty-four hour light-dark cycle. Forcing our bodies to sleep and wake in such unnatural patters unmistakably impacts human physiology, leading to associations with all kinds of different diseases from obesity to cancer to heart disease.
Movement and Exercise
We’ve known for a long time that exercise is important. But what isn’t so known is the recent research indicating that going to the gym isn’t an adequate solution. If we look at exercise from an ancestral perspective, we see that our ancestors moved all the time. They walked an average of 10,000 steps a day. They didn’t sit for long periods and they stood more than half the day. In between, they chased prey, ran from predators, and built things.
This non-exercise physical activity may be more important than the regimented workouts we are familiar with today. If you work at a desk but go to the gym three or four times a week, you’ll meet the conventional guidelines for exercise, but you will still be at increased risk of disease because of all that sitting. Even marathon runners in training who spend most of the rest of their time sitting, have an increased risk of death and disease (Mohlenkamp et al. 2008).
People who walk or are active doing gardening, chores, or manual labour in addition to exercise have a much brighter outlook than those who just exercise. If someone is inactive its more important for them to reduce the amount of time they are sitting than it is for them to start a workout routine.
-------------------------------------------
The modern diseases that countless people suffer from today, like heart disease, diabetes and many autoimmune diseases, were nearly nonexistent in hunter-gatherer populations. Its tempting to think that that’s because hunter-gatherers didn’t get old enough to develop those diseases, but this isn’t true. The average lifespan of people living in Paleolithic hunter-gatherer cultures was shorter than our average lifespan today, but those averages don’t take into consideration the much higher rates of infant mortality and premature death from trauma, warfare, exposure to the elements and complete lack of emergency care. Anthropologists have found that when hunter-gatherer cultures have access to even the most basic form of emergency medical care, like a clinic half a day’s hike away, they live lifespans that are roughly equivalent to our own. The difference between these contemporary hunter-gatherers and us is that they reach old age without acquiring the plethora of chronic modern diseases that we suffer from in the industrialised world.
This mismatch between evolutionary inheritance and our modern environment lies at the root of chronic disease. This mismatch is causing a massive health crisis in the Western world that our current health systems are ill-equipped to manage. To address this, we need to adopt diet and lifestyle behaviours that acknowledge that we evolved to survive in an environment very different from the one we live in today.