Those who’ve been following my blog for some time know that my writing is always based on an evolutionary perspective on human health. But why do I think it’s so important to learn more about the ancestral environment and lifestyle and the selective pressures and natural selection that made our species what it is today? The evolutionary biologist Theodosius Dobzhansky published in 1973 an essay titled “Nothing in biology makes sense except in the light of evolution”, and I truly believe that this idea also applies to all other aspects of life. Without looking at human life in an evolutionary perspective, we’re grasping in the dark when trying to determine what to eat, how to exercise, and in general – how to live our lives in the best way possible. While we don’t have to emulate the lifestyle of hunter-gatherer populations or non-westernized people, we can learn a lot by simply studying the way humans have lived for millions of years. If we learn more about the ancestral natural environment in which our genome was forged, we can create a framework for understanding the gene-environment mismatch we’re now facing in the modern world. In this post I’m going to bring together some of the knowledge we have about hunter-gatherer tribes and non-westernized people, and summarize what we know into a few primary takeaways.
The ancestral natural environment
The paleolithic age is a prehistoric era of human history that stretches from the earliest known use of stone tools about 2.6 million years ago, up until about 10000 years ago. During this time, humans lived as hunter-gatherers that subsided on wild animals and plants. While we don’t have data to really say for sure, it’s generally believed that the paleolithic man was healthy and fit and virtually free from diseases that are running rampant in the modern world. While the average lifespan was shorter than it is today, this low life expectancy is thought to result from high infant mortality, infectious disease, warfare, accidental deaths, etc.
And this is where we get to the root of the paleo philosophy. While there wasn’t one universal prehistoric lifestyle, environment, or diet, it’s generally accepted that the paleolithic way of life is characterized by regular sun exposure, moderate-high amounts of physical activity, “microbial exposures”, and a high-quality ancestral diet composed of wild foods – all things that set you up for a healthy and fit body. The basic idea behind the paleo philosophy is that the ancestral environment is the default/natural human environment and that the ancestral lifestyle promotes a normal phenotype.
It’s this ancestral natural environment that forged both our human genome and the microbiome, but what we’re now learning is that although our human genome changes slowly, the human microbiome adapts rapidly to changes in environment and lifestyle. In many ways, this can be thought of us a hard-wired mechanism that allowed the human species to rapidly adapt to new environments. This is especially relevant in terms of nutrition, as the gut microbiome can adapt to break down a wide range of food ingredients. This is one of the reasons why I’m not convinced that eating a paleolithic diet is necessary to optimize health and well-being. There’s no doubt that basing your diet around an ancestral dietary template is a good idea, but there’s little evidence to suggest that all of the foods introduced after the agricultural revolution are bad for you.
However, it’s no doubt that we would benefit greatly from returning to our roots by getting more sun exposure, being more physically active, getting dirty once in a while, and in general – living more like our paleolithic ancestors (to the extent that is possible and practical in the modern world).
Hunter-gatherer tribes and traditional non-westernized populations are healthy and fit
But how do we know that this ancestral lifestyle optimizes gene expression? The paleolithic way of life certainly involves many of the factors that are known to promote good health, but our knowledge about the paleolithic man is too limited to make firm conclusions about their health. Here’s where we have to turn our attention towards more contemporary times. Humans slowly started to settle down and domesticate plants and animals about 10000 years ago, and most people now live in industrialized settings. But not everyone has abandoned the old ways of doing things. Some populations are still virtually unaffected by the western lifestyle, and some have even kept their ancestral lifestyle up until this day. Most of these indigenous tribes are slowly disappearing, but their health and lifestyle have been documented by researchers over the last centuries – making it possible to draw more accurate conclusions than we can by simply looking at archeological records from thousands of years ago.
Perhaps the most striking thing these studies show is that pretty much all hunter-gatherer tribes are virtually free from the so-called diseases of civilization (1,2). To a certain extent, these findings also apply to semi-nomadic people, traditional horticulturists, and other populations that have kept most aspects of their traditional lifestyle (3,4). Let’s take a look at some of these traditional populations.
Non-westernized populations that have been studied in modern times
The Hadza Bushmen
Who: One of the last true hunter-gatherer communities in Africa. Only about 200-300 Hadza still live as hunter-gatherers. “The Hadza live in small mobile camps with fluid membership, usually comprising a core group of ~30 people, and target native wild foods, both hunted and foraged, for the bulk of their subsistence. While the Hadza are a modern human population, they live in a key geographic region for studies of human evolution and target resources similar to those exploited by our hominin ancestors. The Hadza lifestyle therefore is thought to most closely resemble that of Paleolithic humans” (5).
Health: Low incidence of modern diseases
Diet: Meat, honey, baobab, berries, and tubers. Seasonal availability determines macronutrient intake. Men eat more meat and honey, and women eat more plant food.
Lifestyle: Plenty of sun exposure, low-moderate levels of physical activity, and plenty of microbial exposures (e.g., dirt)
More information: 6,7,8
Image source (Photographer: Martin Schoeller)
The Kitavans on the Island of Kitava (Horticulturalists)
Studied in: 1989 by Staffan Lindeberg et al.
Who: One of the last populations on Earth with dietary habits matching that of our prehistoric ancestors.
Where: The island of Kitava, one of the Trobriand Islands in Papua New Guinea’s archipelago
Health: No indications of stroke, acne vulgaris, overweight, diabetes, dementia, or congestive heart failure. Excellent blood pressure, etc.
Diet: High-carbohydrate ancestral diet (69% carbohydrate, 21% fat, and 10% protein) made up of root vegetables (yam, sweet potato, taro, tapioca), fruit (banana, papaya, pineapple, mango, guava, water melon, pumpkin), vegetables, fish, and coconuts.
Lifestyle: Moderate amounts of physical activity, regular sun exposure, some smoking, and little access to modern hygiene and pharmaceuticals.
More information: 9
Who: A group of culturally similar indigenous peoples.
Where: The Arctic regions of Greenland, Canada, and the United States
Health: Virtually free from chronic disease when living as hunter-gatherers. The health of modern Inuit has quickly deteriorated as they’ve started adopting the western dietary pattern.
Diet: The traditional diet of the Inuit consists primarily of seafood, land mammals, and birds. There’s some controversy regarding the composition of the Inuit diet, but it’s generally accepted that the traditional diet is high in fat (up to 75%) and low in carbohydrate. The fact that the Inuit stay so healthy on this type of “extreme” diet is sometimes referred to as the Inuit Paradox.
More information: 10,11,12,13
The Maasai (Pastoralists)
Who: A Nilotic ethnic group of semi-
Where: Southern Kenya and northern Tanzania.
Health: Low incidence of diseases of civilization. Maasai have slowly adopted aspects of the western lifestyle, and as a result, their health has deteriorated.
Diet: Some controversy, but most reports suggest that the traditional diet of the Maasai is primarily composed of milk, meat, and blood.
Lifestyle: Moderate-high amounts of physical activity, regular sun exposure, and little access to modern hygiene and pharmaceuticals.
More information: 14,15
What are the primary takeaways from the studies of hunter-gatherer populations and non-westernized people?
- The ancestral environment could be classified as the default/natural human habitat. We can adapt to a wide spctrum of environments and lifestyles, but when we diverge too far away from the ancestral natural environment, our health declines.
- The default state of Homo sapiens is one of good health and protection from diseases of civilization.
- The gene-environment mismatch we’re now facing in the modern industralized world is the primary cause of diseases of civilization.
- Although our human genome changes slowly, the human microbiome adapts rapidly to changes in environment and lifestyle. This is most relevant in terms of diet.
- Humans can be lean and healthy on a wide spectrum of diets.
- Common characteristics of a healthy lifestyle: Good nutrition, adequate sun exposure, acute stress (not chronic), low exposure to pollutants, regular physical activity, plenty of time spent outdoors, good sleep, and “microbial exposures”.
In the end I want to emphasise that although I believe we can learn a lot by studying hunter-gatherer populations and non-westernized people, I’m by no means suggesting that we should abandon all aspects of our modern lifestyle and return to the wild (Unless that’s something you want off course). The ancestral way of life can often be harsh and unforgiving, and most people are probably going to prefer the comfortable modern environment. However, by combining the best from the ancestral lifestyle (e.g., dietary practises, sun exposure, physical activity) with the things we cherish about the modern life, we can get many of the same health benefits as our prehistoric ancestors while not having to sacrifice the assistance of modern technology.