What Captive Gorillas Can Teach Us About Health & Medicine

two gorillasImagine 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.

Picture: Creative Commons picture by Martha de Jong-Lantink. Some rights reserved.


  1. Absolutely true! We are evolving too rapidly for our internal genetic and microbial environment to keep the peace within us. This has only resulted in a dependance on the adage “a pill for an ill” to accommodate our resulting difficulties. Thus, chronic disease has set in amongst the many, and too few of us have realized that a return to the old ways is the very cure we need to get ourselves back on track. Thank you for spreading the health!

  2. Great post! We also have to consider that grains do not run away and we don’t need any superior fitness and health level to survive and reproduce with neolithic food. The alleged “adaptations” to new foods is a mere selection that took off who couldn’t survive enough to reproduce with them. This is the major misunderstanding. Where’s the strong selection pressure that we had during the 2My of evolution in nature that shaped our genome? If you die off in your 60s or 70s when you already had all the sons you wanted, there’s no selection. And with modern medicine there’s even less one. And even if there was a pressure, complex mutations that allow a species to thrive with a completely new food, need time. It’s been estimated an average of 2My for a “complete” speciation. How long it would take for humans to change their gut? And without nutrient dense food we should also pay a bill, our brain! Coming back to chimps or something else…

  3. Good analogy. We need to look at human health and behaviour though the lens of ethology instead of always seeing us as “other” from the other animals.

    Regarding the fundamental premise of the paleo/ancestral movement, I’m starting to have some reservations. While we can safely state that we are certainly maladapted for the post industrial/Information Age, I’m not too sure that we have not been influenced by selection pressures after the agricultural revolution.

    Certain populations for example the Chinese are a relatively new population which blossomed due to the advent of rice agriculture. For a population whose populational success was so dependent on rice, one can’t help but ask if eating rice is more helpful than harmful for the individual’s reproductive success.

    Would love to hear your thoughts on this..


    • Hi Sam!

      You raise some interesting points.

      Here’s the key thing to keep in mind (which a lot of people seem to forget when discussing Paleo, evolution, ancestral health, etc.): Natural selection only favours traits that improve health and well-being if they are also linked to the reproductive success of the organism.

      For example, just because some people have evolved the capability to digest lactose as adults doesn’t necessarily mean that drinking milk is healthy for them.

      “Every” population that has adopted agriculture has experienced rapid population growth. That doesn’t necessarily mean that people got healthier. Actually, as we know, the opposite is often true.

      That being said, I agree with a lot of what you’re saying. We obviously didn’t stop evolving 10000 years ago. Moreover, as I’ve pointed out in many of my articles, we all harbour a highly malleable microbiome that can adapt rapidly to environmental changes (e.g., diet).

      I think you may find my latest article on cereal grains interesting.

      Thanks for your comment!

  4. Alessio says:

    Of course rice, as the other grains, are good for the “success” of our species, but the “evil” lies in the meaning of success itself. Reproductive chance seems to be link to the availability of food, especially of sugars. Indeed, it seems that women started to be all year round fertile since the advent of such stable availability of starch. And in a certain sense, as you can also read on the paper of Cordain and Eaton “cereal grains: a double edge sword”, it allowed an explosion of the human population. Unfortunately, it says little about the long term health. If you are in nature, the more you are fit, the more you have the chance to reproduce. And this drives the selection. Every dork is able to raise a crop, look at Nazi’s prisoners, they were able to work despite a striking undernourishment and terrible conditions.
    And as soon as agricultural communities settled down, we can say that there has been a selection that took away the genes pool not able to survive under such conditions. But took away the choice of the fitness success, also because mating started to be more linked to a social class issues instead of natural fitness.
    I agree that asians survive very well, but, have you seen the average asian grain based people? Far from being fit as an hunter gatherer… Using history is also a good tool to have a picture of the puzzle. What’s the most powerful army? Gengis Khan didn’t have a rice based diet…mostly meat and dry blood. Any respectable warrior had a “paleo” style diet, like is being recognized by top athletes nowadays.
    Thriving is not surviving.

  5. Alessio says:

    Someone who criticized the paleo diet pointed out that the more the selective pressure is high, the faster is evolution. This is inaccurate as well, because it takes for granted that a species is going to evolve anyway. It depends on the magnitude of changes required by the new environmental change. If to match the new environmental variable you require X mutations but you can only have n mutations at time slot to be selected, you require a certain amount of time, and in our case it should be established how many changes we require, how many mutations at time we may have also related to the population size, and make a model to predict, under a selective pressure, how long it would take for such mutations to be fixed in all the population. If the aformentioned statement was true, i.e. with enough pressure any species evolves quickly, dinos would be still here.

  6. Alessio says:

    If you grow your crop, you are not doing seed predation as granivores, you don’t have to be strong and healthy, you don’t hunt a large mammal 10 times stronger than you, you don’t have to escape from a hungry lion. You choose your partner and have all the sons you want that will help you to grow your grains. Who cares if you develop a chronic disease after some decades? Your partner didn’t choose you because you can kill a mammouth. With modern medicine, we relaxed the pressure even more. Almost everyone can survive, almost any genetic pool may be kept if you fix the issues with drugs. But again, please tell to a western 70 years guy to chase a gazelle like if he was Bolt, and then climb a tree to pick up honey or walk 20 km every day in the middle of Kalahari desert. Anyone who wants to try here?

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