Imagine standing in the middle of a rainforest taking in all of the stimuli around you; the sound of birds singing, the rustling of leaves in the light wind, and the sight of a monkey high up in one of the many trees around you. The immediate impression of such a scene might be that nature is first and foremost a peaceful place where animals, plants, bacteria and other organisms co-exist silently, side by side.
However, when you start to look more closely, you realise that your first impression was probably biased by your preconceived notions of such natural environments as beautiful, pure and untouched by the mark of man. We clearly know that there are predators out there and that not all creatures live side by side in friendship, but I think few of us look at life for what it really is: a struggle for existence in which organisms compete for resources and need to adapt to keep up in nature’s arms race.
For most humans today, dangerous animals and food procurement are far down the list of daily concerns, but for other organisms (and also for our species not long ago), the battle for survival is a dominant component of life. Darwin opened us up to this fact in his book “On the Origin of Species”, in which he formulated his brilliant – but simple – idea of natural selection; the process by which organisms that are better adapted to their environment tend to transmit more of their genetic characteristics to succeeding generations than do those that are less well adapted.
So, you might ask, if humans today are so cut off from nature that we no longer have to struggle to survive and reproduce, why should we consider evolutionary theory in the discussion of health and fitness? The reasons are many…
The consequences of taking an organism out of its natural habitat
Imagine that you’re a zoo manager who somehow gets permission to transfer four of the gorillas from the rainforest mentioned in the beginning to your zoo. Since you’re just a regular guy who doesn’t care or know much about biology or nutrition, you don’t pay that much attention to what type of environment gorillas are best adapted to live in. Although you’ve taken some measures to replicate part of their natural habitat – largely in an attempt to make the human visitors that come to your park get a feeling of being “in the wild” – you clearly realise that the living conditions in the zoo are very different from those of a tropical forest.
After a while, new gorillas that are born into captivity become a part of the mix, which prove to be a booster for the zoo’s popularity. All seems to go well until one day when one of the initial four gorillas dies suddenly of heart failure. This triggers you to take a closer look at the health and well-being of the gorillas, and you realise that a lot has happened since you first acquired those four first gorillas from the wild. Of course, you had noticed that they had started getting a little puffier over the years, but it isn’t until now that you realise how bad things have become.
Those gorillas that were born into captivity look very different from the ones you transferred from the wild a while back, and you realise that overweight, heart disease, and other disorders that you long thought of as “human” problems have become a major issue for the gorillas. When you ask the zookeeper in charge what’s going on, he just says that these diseases are “normal” among captive gorillas and that he’s been doing what is done in many other zoos, including feeding the gorillas a diet high in starch, sugar, and added vitamins (1).
Since you’ve seen how gorillas look when they live in their natural habitat, you don’t leave it at that, but rather investigate the issue further. You realise that it could be something wrong with the gorillas’ living conditions, and that one possible solution to their health problems is to change their environment in some way. Since wild gorillas seem to be so damn lean and healthy, you simply instruct the zookeepers to adjust the environment in the zoo so it is more similar to the rainforest from which the first four gorillas came.
Perhaps most importantly, their starch- and sugar-heavy diet is replaced with a species specific diet that consists of lettuce, dandelion greens, bark, leaves, and other foods gorillas have been known to eat in the wild. After a short time on this new diet, the gorillas quickly start dropping body fat, and illnesses that are common among captive gorillas but rare among their wild relatives start decreasing in prevalence (1).
Old genes in a modern environment
With the exception that we are free to move around the world, we humans are in a very similar situation to that of sick gorillas in a zoo. Many of us consume evolutionarily novel foods, we don’t move our bodies enough, and powerful cultural evolution has also altered our sleeping patterns, stress levels, and many other parts of our life at a rapid pace.
While someone who transfers gorillas from the wild to a zoo can clearly see how the transitioning process goes, the shift from a hunter-gatherer way of life to life to that of an office worker in the 21st century has occurred over hundreds of generations, and as such, we have never witnessed an immediate change. We’re like the baby gorillas in a zoo in the sense that the world around us is all we have ever known, and it’s therefore easy to look at today’s living conditions as completely “normal”. However, from an evolutionary perspective, many parts of our modern lifestyles are abnormal and novel, something that is important to consider in the discussion of health and fitness.
For millions of years, our ancient ancestors were very much a part of the battle for existence in nature, and natural selection acted to adapt their bodies to conditions that differ markedly from today’s milieu. Just like other organisms, we’re genetically adapted to live under certain environmental conditions, and when we change these circumstances at a pace that is too rapid for natural selection to keep up, evolutionary mismatches occur. In the modern world, this mismatch between biology and environment primarily manifests itself as diseases of civilization, such as cardiovascular disease, myopia, obesity, and type-2 diabetes (2, 3). We live in an environment for which we’re not well adapted.
Genetic differences and variations in microbiome structure and diversity between humans today do play a role in determining how we should design our diet and lifestyle. However, the fact is that we all descend from the same ancestors that lived in Africa in the Paleolithic era, and although we today wear suits and dresses and work in large office buildings, our inner hunter-gatherer is still with us in the sense that “the portion of our genome that determines basic anatomy and physiology has remained relatively unchanged over the past 40 000 years” (4). Evolutionary theory and the premise that we’re to a significant extent still Stone Agers from a genetic perspective are what lay the basis for good scientific studies and papers within several different fields of health & medicine, such as sports physiology, nutrition, and psychology (5, 6, 7).
The human microbiome changes much more rapidly than the human genome, which partly explains why we are able to introduce previously novel foods into our diet. However, it’s important to note that this type of adaptation is primarily relevant in the discussion of diet, not so much in all of the other lifestyle factors we talk about in the ancestral health community, such as sleep, exercise, socialization, sun exposure, and stress.
All in all, we do have to take individual variation into account, but the fact is that we are all genetically very similar, and we all carry a Paleolithic legacy within us.
Nudging our modern lifestyle in the right direction
Natural selection only favours traits that improve health and well-being if they are also linked to the reproductive success of the organism. In other words, evolution doesn’t necessarily provide a clear-cut answer as to exactly how we should eat or exercise for optimal health. However, as everyone in the ancestral health community knows, looking back at our evolutionary history gives us a very good indication of what types of diets, exercise routines and so on for which we are best adapted – an understanding that lays the basis for designing a healthy lifestyle.
Just like captive gorillas experience rapid health improvements when their way of life is adjusted to better match that of wild gorillas, we too should aim to adjust our modern lifestyle – including our sleep, diet, physical activity, microbial exposure, sun exposure, exposure to harmful substances, stress and so forth – to more resemble that of foragers and traditional populations who live in environments that are better matched with human genetics.