You Only Need One Diet

It’s the human diet. One size really does fit all.


When it comes to diet, it is often said that one size does not fit all. Different people fare better on different diets. I demur on this: one size — with a few personalized tweaks here and there — really does fit all. That may not be a popular stance, but I shall now set out the case for the defence.

Throughout the course of evolution many species of humans have roamed this globe, often coexisting. How strange it must have been, to occasionally encounter those “others.” But today we are alone, the last remaining species belonging to the Homo genus, which emerged over two million years ago. Sapiens is literally the last Homo standing.

Meet the family

When in 2003 the mapping of the human genome was completed, the heartening discovery was made that we are all related to each other. We modern humans can trace our origins to East Africa, our ancestral homeland. That is where Homo sapiens appeared, 200,000–300,000 years ago. We began to move into Asia something like 50,000–80,000 years ago. Before you knew it, we were everywhere, and doing a remarkable job of adapting and surviving.

The genes we carry today were determined in Africa. We are little changed since the end of the Paleolithic era, which represents 99.5% of human history. Our ancient genome has an average mutation rate of 0.5% per million years, meaning it “still resides for the greater part in the Paleolithic era.”

And so to food, and what to eat.

In order to answer that, we need to understand the “nutritional milieu” in which the genetic make-up of H. sapiens was established.

That is not to say that we should all be eating what is often referred to as the “Paleo” diet. Essentially, there is no such thing. Much of our success as a species can be ascribed to our adaptability to whatever environment we settled in as we migrated away from our original homeland. The menu varied wildly.


The out-of-Africa exodus occurred primarily along coastlines and rivers, and from lake to lake across North Africa. Consequently, anatomically modern humans regularly consumed fish and shellfish, high in protein and providing the micronutrients that are crucial for brain growth and development, including the fatty acid DHA, iodine and vitamins D and B12.

Meat was a dietary staple, especially for those who migrated further inland, providing high quality protein and fat, and highly bioavailable minerals, including iron and zinc. Skeletal analysis — the study of fossil isotopes — makes evident that “..even very early hominids consumed a considerable proportion of meat in their diets.”

The further north of the equator humans travelled, the less plant food was consumed, as it became less available.

Whatever their environment, all wild animals eat in accordance with the practice of “optimal foraging”. Optimal foraging is a behaviour whereby energy (calories) obtained from food must be greater than the amount of energy expended procuring that food.

Optimal foraging is about efficiency. You can’t spend all day, and all your energy, gathering a few leafy greens and berries when you have a hungry tribe back at camp to feed. Even today, hunter-gatherers show a strong preference for animal-based foods over plant-based foods, even when living in vegetation-rich environments.

That would also explain the attraction of junk food: lots of filling calories for little expenditure. It fits the paradigm of modern optimal foraging perfectly.

Our first mistake

In 1987, scientist and author Jared Diamond published his now famous article in Discover magazine, entitled The Worst Mistake in the History of the Human Race. He was talking about the first Agricultural Revolution that began around 10,000 years ago, when sapiens transitioned from a hunter-gathering to a settled, farming lifestyle. In his article he states:

“In particular, recent discoveries suggest that the adoption of agriculture, supposedly our most decisive step toward a better life, was in many ways a catastrophe from which we have never recovered.”

Agriculture changed the course of history, arguably more than any other human-driven event. The Neolithic era was characterised by a (gradual) switch from a highly varied, meat-based diet to a monotonous, cereal-based diet. A typical farmer’s diet in Neolithic Europe consisted mostly of bread made from wheat or other grains like rye and barley, supplemented with peas and lentils, milk and cheese, some occasional meat, and seasonal fruits.


The transition from a meat-based to a cereal-based diet resulted in numerous detrimental health effects, including reduction in stature, increase in infant mortality, reduction in lifespan, increase in iron deficiency anaemia, dental decay and bone mineral disorders, including osteomalacia.

Much-reduced protein consumption was a major feature of the Neolithic and contributed to a process called gracilization (thinning) of the skeleton. Pre-agricultural people had much greater bone density than we do today.

The Agricultural Revolution was one thing. Then came the Industrial Revolution, thousands of years later, but just seven or eight generations ago.

The Industrial Revolution gave rise to a completely new source of human nutrition: the processed food industry.

Since the start of the twentieth century, sugar consumption has rocketed, as has vegetable oil consumption, having largely replaced the animal fats traditionally used as a cooking medium. These novel vegetable oils are ubiquitous in processed foods. They are rich in omega-6 fatty acids that compete with, and displace, omega-3 fats (DHA) in the brain. Fish is the major source of DHA, and fish consumption has plummeted to levels well below the recommended amount in both the UK and the US.

As this extraordinary nutrition transition permeated the twentieth century, so too did its running mate, the disease transition.

Until the early 20th century, infectious diseases such as tuberculosis were the main cause of death following the post Neolithic era. By the mid 20th century, chronic diseases (diabetes, obesity, heart disease, cancer) had emerged as the number one threat to global health. Mental illnesses have increased in line with physical chronic diseases since 1960.

There has also been a transition in the advice we are expected to follow. Instead of consuming the diet that humans ate throughout evolution, experts now tell us to avoid or cut down on meat and saturated fats such as butter, and switch to those new, refined vegetable oils and cereal grains.

The 2017 U.S. Department of Agriculture report, US Trends in Food Availability, reveals that Americans have complied well with official dietary guidelines. Between 1970 and 2014, red meat consumption decreased by 28%, with overall saturated fat consumption down 27%. At the same time, vegetable cooking oil consumption rose by a staggering 248%. Consumption of grains, in the form of wheat flour, rice, corn, oats and barley, increased by 28%. Americans still consume 83% more than the recommended limit of 12.5 teaspoons of sugar per day.


Along with chronic diseases, something else is starting to surface, something less visible but arguably more sinister. The human brain is shrinking, as confirmed by a body of research that has been accumulating since 1988. This shrinkage — atrophy — began during the Epipaleolithic period, which was the transitional period between hunter-gathering and agriculture, and remains an ongoing phenomenon. Over the last 20,000 years, average brain size has decreased by 10%. What’s even more alarming is that the last 4,000–6,000 years have witnessed an acceleration of this atrophy.

Various theories have been proposed to explain this startling development, but no one cause has been established. I would hazard a guess that diet is involved.

Healthy hunters

If we assume that our current dietary habits are killing us, it surely makes scientific sense to take a close look at the overall health and diets of modern tribal peoples whose lifestyles remain largely uninfluenced by the western world.

Their way of life is under threat, which means we are all under threat. According to Survival International, the global organization that advocates on behalf of tribal peoples, “…tribal peoples are better at looking after their environment than anyone else.”

“Uncontacted peoples are supreme conservationists with the lightest footprint on our planet, and they protect some of the world’s last and most biodiverse forests. They have developed extraordinary skills and have unrivalled knowledge of their universe.” (Fiona Watson, Survival International)

We can learn from tribal peoples, but we need to be quick; most today are in transition between their traditional lifestyles and modern living.

Hair and blood analyses have shown that before the 1960s, the nutritional status of various tribal peoples (the !Kung, the Aka of the Central African Republic, aboriginal Australians and the northern European Sami) were within healthy ranges.

Approximately 15 years later, following settlement, these people had started to experience high rates of iron deficiency anaemia. Post-transition deficiencies in folate, iron, vitamins A, E and B12 were also observed, alongside an increase in diabetes, obesity, cardiovascular risk and cancer.

The nutrition transition phenomenon works in reverse. A paper published in 2009 in the European Journal of Clinical Nutrition detailed a small study that investigated the effect of a diet, similar to that consumed by preagricultural hunter-gatherers, on sedentary, slight overweight adult Americans. After following the diet for just ten days, all the volunteers experienced dramatic improvements in health markers, including “significant reductions” in blood pressure, improved arterial flexibility, improved insulin sensitivity, and lower blood fat levels. The diet consisted of lean meats, vegetables, fruits and nuts, and excluded cereals, dairy and legumes.

“Considerable evidence suggests that many common diseases can be prevented by hunter-gatherer diets.”(Lindeberg 2009)

In 1985, anthropologists S Boyd Eaton and Melvin J Konner proposed their “discordance hypothesis”, which states that the human genome is determined by the conditions of the Paleolithic era, and that changes have occurred too rapidly for us to adapt, resulting in a mismatch that leads to chronic disease.

“The physical activity, sleep, sun exposure, and dietary needs of every living organism (including humans) are genetically determined. This is why it is being increasingly recognized in the scientific literature, especially after Eaton and Konner’s seminal publication in 1985, that the profound changes in diet and lifestyle that occurred after the Neolithic Revolution (and more so after the Industrial Revolution and the Modern Age) are too recent on an evolutionary time scale for the human genome to have fully adapted.” (Carrera Bastos et al)

There is no one diet that characterises pre-agricultural humans, who ate from a fabulously broad menu, according to geographical location. However, there were commonalities. These include:

  • High wild meat/fish intake with a preference for fatty prey
  • Rare consumption of cereal grains
  • No added sugar
  • No refined vegetable oils
  • Extensive range of wild plant foods, where available.

We cannot go back to a hunter-gatherer lifestyle — there are way too many of us, and in any case we lack the skills to do so. And who would choose to? But if some cataclysmic event (which may be coming) left us with no choice, we in the post-industrial world would not survive for long. We really do need to learn some ancient skills from tribal peoples.

The catch-22 dilemma is that neither can we continue to consume a diet that is making us sick, shrinking our brains and shortening our lives. We need to eat in a way that most closely resembles the diet on which we evolved. And is realistic.

There are several popular diets that fit this paradigm: the ketogenic diet, the Paleo diet, the Atkins diet, the ancestral diet, the low GI (glycaemic index) diet. Perhaps you could add a few more. Like the pre-agricultural diet of humans living all around the globe, these diets have their differences and their similarities. Paleo adherents don’t eat dairy foods, because they are a product of agriculture, and a recent addition to the human diet. Ketogenic fans love dairy foods, because they are so full of saturated fat.

But whatever their differences, all these diets are based on a low carbohydrate, high fat and/or protein way of eating, without sugary snacks and other processed “food”. And they are all as close as we can realistically get to the pre-agricultural diets of our ancestors, the one to which we are genetically adapted.

We Homo sapiens all require exactly the same nutrients, the same ones we’ve always needed. How much depends on age, level of physical activity, exposure to sunlight, geographical location, and so on. Some people have allergies or sensitivities to certain foods that they need to avoid. But nobody needs sugar, cereal grasses, vegetable oils et al.

As members of the Homo sapiens species, we all thrive on the same range of foods. You could call it the human diet.

Our technologically-driven, industry-centric lifestyles have left the vast majority of the global population so disconnected from the natural world that we can no longer see or understand our place within it. We live and think outside our natural context, and even accept absurd claims, such as fake meat substitutes, assembled in laboratories and factories, being healthier than the real thing. We choose foods that are nutrient-poor, and then buy factory-produced supplements to compensate for the shortfall.

You can change your diet as often as you like, and your food-based ideology. But you cannot change human evolutionary biology. One, broad-ranging size really does fit all.

Source: Article by Maria Cross MSc (

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