A recurring theme on this blog is how the health status of our species has changed over the course of evolution, with an emphasis on the agricultural and industrial revolution. If you’ve read my articles on nutrition, exercise, and human health you know that the facts are clear; the western diet and lifestyle aren’t doing us any favors. Yes, modern science and technology have helped us combat many infectious diseases, but recent advancements have also allowed us to create living conditions, foods, and drugs that have a negative impact on our health. Also, I want to emphasise that although most people will agree that the decreased infant mortality, increased lifespan, and low rates of infectious disease we’re now seeing in the industrialized world are a good thing, the fact is that we have essentially eliminated many of the selective pressures that shaped our species for millions of years; a change that doesn’t come without consequence. Also, the data are clear, although average lifespan in the developed world is relatively long, we aren’t healthy. Obesity, acne vulgaris, cardiovascular disease, colorectal cancer, and many other chronic disorders run rampant in the modern world, and very few people live a disease free life anymore. Since most of these chronic disorders were/are virtually absent in hunter-gatherer communities and some isolated populations, they have been classified as diseases of civilization.
If we really think about it, the fact that hunter-gatherers are free from these health conditions makes absolute sense. Humans are just another species on this planet, and just like other animals are lean and fit when they live in their natural habitat and eat the food they are adapted to eat, humans are also healthiest when we live in an environment that isn’t too different from the natural habitat in which our genes were selected. Also, just like domesticated animals get sick when they are confined to unnatural living conditions and don’t get the food they are adapted to eat, human health deteriorates when we eat processed diets, don’t exercise, and in general, live in a way that isn’t consistent with our evolutionary heritage.
So, it’s clear that if we study the ethnographic data and look at how the human species has evolved for millions of years, most of the chronic diseases we now see in the modern world are not a natural part of human life. On the contrary, the “default”/natural state of Homo sapiens is one of leanness and good health. Definitely not lean like a fitness competitor or free from infections and occasional illness, but overall good health. However, I want to emphasise that this clearly doesn’t mean that we should completely abandon the modern way of life and try to emulate the hunter-gatherer lifestyle. Hunter-gatherers lived in a harsh and unforgiving environment, and warfare, accidents, infectious disease, and dangerous animals were just some of the many threats they faced. However, there is no doubt that looking at our prehistoric ancestors can help us understand what types of diets, activity patterns, etc. we’re genetically adapted for.
The connection between environment and DNA
So, if you’re familiar with the literature (or have read my articles on the subject), you know that many of the “advancements” that have occurred since the agricultural revolution also come with some adverse effects. But what is really going on? How are these changes impacting our health, and why does the prevalence of diseases of civilization keep increasing so rapidly? To get to the root of these questions, we have to look at the very thing that makes us who we are; DNA. While it was long believed that our genetic material was just a static code that stayed with us throughout life and was passed onto our children, we now know that DNA is more of a fluid material that interconnect organism and environment.
I’ve previously highlighted that we’ve got two genomes in our body. We’ve got the human genome, which is the collection of human genes we inherit from our parents, and we’ve got the human microbiome, which is the collective genomes of all the microorganisms that live “in” and on our bodies (skin, GI tract, lungs, etc.).We’ve also got the epigenome, which is not a collection of genetic material per se, but rather the epigenetic tags that are left on our human DNA. Epi means above, essentially implying that the epigenome is “above” the human genome. To understand what I want to convey with this post, let’s review the facts:
The human genome
- While there have been some minor adaptations since the paleolithic era, the fact is that our genes were primarily selected for in the ancestral environment (1,2). This is to be expected, as the 10000 years that have passed since the agricultural revolution is just a “drop in the sea” compared to the hundreds of thousands of years we lived as hunter-gatherers.
- Environment and lifestyle have a significant impact on gene expression, which means that we can influence which genes that are upregulated and which ones that are downregulated. Some of these changes in gene expression are heritable in the sense that epigenetic marks are passed on to offspring. Diet, exercise, and exposure to pollutants are just some of the many things that impact these epigenetic processes, and it’s clear that sedentary living, processed foods, and many other factors associated with the modern lifestyle negatively impact gene expression (3,4,5).
- The so-called diseases of civilization are thought to result from a gene-environment mismatch, meaning that we’re not genetically adapted to the “modern environment” (emphasis on the western diet and lifestyle) (1,2).
The human microbiome
- Processed diets, pharmaceutical use (especially antibiotics), excessive hygiene, “disconnect” from nature, and many other aspects of the western lifestyle perturb the microbial communities in and on our body.
- We’ve probably lost some key species that used to be a part of the ancestral microbiome.
- Hunter-gatherers and people who live in rural communities generally have higher levels of microbial richness and increased biodiversity compared to individuals living in the industrialized world (6,7).
- The modern cosmopolitan lifestyle probably resulted in a dramatic change to the human gut microbiome (8).
- The microbiome is seeded before birth, and we continue to receive microbes from mom through breast milk, skin contact, etc. (9). Since the microbiome harbors most of the unique genetic material in our body and provide many essential functions we can’t do without, this transfer of microbes (and their genes) could in many ways be as important as the human genes we inherit (especially in terms of disease susceptibility).
- We receive microbes from animals, other humans, and the rest of the environment (10,11,12). How are the changes to the “global” microbial ecosystem (e.g., widespread use of antibiotics in humans and livestock, depleted soil quality) affecting human health on a population-wide basis?
- The microbiome plays an essential role in human health, and researchers are now linking microbial disturbances (dysbiosis, loss of old friends, etc.) to all sorts of different diseases.
- Although the second genome can adapt rapidly to changes in environment, there is no doubt that the human microbiome is healthiest when we live in a way that is somewhat in consistence with the “ancestral” lifestyle (e.g., not too hygienic, regular exercise, nutrient-dense diet).
When we see all this in one place like this, it becomes abundantly clear what is going on with modern humans and why we’re seeing such a rapid increase in prevalence of obesity, heart disease, cancers, and other chronic disorders. It’s really just the expected response to our way of life. The facts are clear, many aspects of the “modern” environment and the western diet and lifestyle (e.g., sedentary living, processed diets, antibiotic use) negatively impact our physiology and health by influencing gene expression and the balance of microorganisms that colonize our body (and thereby the microbial gene catalogue). Also, since epigenetic marks and microbes are passed on to offspring (and in the case of microbes, also between people), there’s no surprise that the incidence of chronic disease keeps rising.
It’s clear that if we look at lifestyle diseases from a global perspective, the evolutionary tale is one of degeneration. This declining health status primarily began with the agricultural revolution and has only worsened over the last several centuries.
Taking responsibility for our health – and the health of our children
All of this might seem frustrating and hopeless, and in many ways it is. However, this knowledge is also empowering in the sense that we can turn these things in a positive direction. It’s likely not happening on a global basis, at least not at the moment. One of the problems is that instead of looking at our past and realising that the so-called diseases of civilization primarily result from a maladaptation, we look for cures, vaccines, drugs, and other fixes. And this is generally the human way, we target the symptoms.
However, epigenetics and the human microbiome are two of the major topics in the scientific community at the moment, and a lot of people are starting to realise that we have to consider the effects our lifestyle has on gene expression and our microbial inhabitants. I just hope we won’t end up with a situation where drugs are considered the solution for tweaking these processes.
Anyways, on an individual basis, all of this does provide each and every one of us with the knowledge we need to take responsibility for our own health. Even though human health on a global basis is declining, that doesn’t mean YOUR health has to. Is it possible to achieve optimal health in the modern industrialized world? No, probably not. It’s pretty damn hard to avoid environmental toxins and pollutants completely, exercise as much as we should, avoid chronic stress, etc. However, that isn’t the goal either. The goal is to combine the best from both worlds (ancestral/hunter-gatherer/non-westernized and the modern world) and find the balance between doing what is optimal and doing what is livable/enjoyable. And as so many folks in the ancestral health community have realised, these things are often the same thing.
Okay, that’s it for today. What do you think of the current human health status, and do you think we can turn this around for the better? Feel free to post your thoughts and feedback in the comment section…
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