The Story of How Fatty Animal Products Made Us Human

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If you go to any modern day grocery store, you’d never realize how sacred and prized fat ever was. 

Hunter gatherers and aboriginal tribes are rolling in their graves when from our obsession with “Low-Fat” diets. 


Because fat made us human. And our ancestors would have KILLED for as much fat as we have available. Actually, they DID kill for fat. 

If you eat the fuel you were evolved to eat, you will thrive.

If you eat the processed sludge you were brainwashed to eat, you will suffer.

Let me briefly explain.

Human Brain Size

The distinguishing factor between humans and our primate ancestors is our brain size.

(Although not all of us were blessed with this adaptation…)

Between 6 million and 2.5 million years ago, our brain size was fairly consistent. Since then, it has quadrupled in size.

Skeleton growth over the years

According to Viljammur Stefansson in The Fat of the Land, the forest lands turned into dry prairies around 2 million years ago from climate change.

The pre hominid diet of fruits and seeds would no longer suffice. The cooler grasslands made plant foods more difficult to procure because of their seasonality .

Some pre hominids just turned to lower quality plant foods. To be fair, this was the easier approach and not even our ancestors were immune to laziness. 

But fossil evidence shows that by 1.2 million years ago, these ancestors of ours died out , while othermore “entrepreneurial” hominids found new ways to survive and obtain sufficient energy.

Man the Fat Hunter and Scavenger

These more enterprising humans started to hunt and scavenge for higher energy animal products.

Anthropological evidence dating back 2 million years ago finds that Homo Habilis — the earliest Homo — used stone tools to obtain food

When predators killed animals, they conveniently left behind bones and skulls that they were unable to extract food from. Fossil evidence shows that the Homo Habilis would fracture the skulls and bones for brain and marrow — two fat sources. 

The meat and fat provided a complete nutrient, protein and fatty acid profile, which allowed the hominids more time for other activities. Increasingly, evidence suggests that this symbiotic relationship between tools, fat, humans and cooperation made us who we are today. 

“Evidence from the human fossil record, and the archaeological record, suggests a process involving increased dependence on technology and learned skills (manufacture and use of stone tools and hunting implements, techniques of food preparation) as well as social skills (cooperative hunting, division of labor, food sharing, a long period of offspring provisioning)”

Our ability to procure energy dense fat gives our body sufficient energy to allow our brain to grow and unlock higher order activities.  

“The advent  of stone tools  as well as the appearance  of stone-tool cut marks on the fossilized bones of prey animals suggests that early members of our genus were increasingly exploiting animal foods as a source of sustenance. This dietary shift from  a predominantly plant based diet to one in which animal foods became increasingly important allowed for the relaxation of the selection pressures that had formerly constrained encephalization in Australopithecus species”

Speaking of, if you want to learn more about the carnivore diet, a diet centered around the most nutritious foods in the world, sign up for my getting started guide below.

Brain’s Energy Requirement

Human brains are unique in how much energy they require. They require so much energy that they could cause climate change…

The human brain uses 20-25% of our resting mHuman brains are unique in how much energy they require. They require so much energy that they could cause climate change…metabolic rate, compared to 9% from other mammals. .

This is why when you don’t have proper nutrition you feel tired. Your brain needs a constant supply of energy. 

Because of the high energy requirement, the only way a brain can grow is if total energy intake increases or if that energy is taken from other tissues.

Evolution “chose” the latter. There was a concomitant reduction in colon size to account for our brain difference.

Relative gut volume by % across different mammals

However, this was only possible because we discovered a highly energy dense form of energy: animal fat. Plant foods require a large colon to ferment and digest fiber into energy. This is precisely why herbivores like Gorillas have a large beer belly looking gut. 

But fat can be mobilized for energy directly from the small intestine and used more efficiently for fuel. 

We made a trade. Plant foods for animal foods. And colon size for brain size. A good trade if you ask me. Almost as good as the United States’ purchase of Louisiana. 

Physiological Limit on Protein Intake

According to MIki Ben Dor, we also needed fat because of the physiological limit on protein consumption .

Using protein for energy requires enzymes in the liver to expel nitrogen. This conversion is limited by enzymes in the liver and the ability of the kidney to dispose urea. 

One study shows that the maximum conversion amount is 3.8 g/kg bodyweight a day. 

Miki believes the maximum caloric intake for protein is closer to 35%, leaving the remaining 65% for animal fat and / or carbohydrates. However, given the dearth of carbohydrates available and our reduced colon size, the only plausible consistent energy source was animal fat. 

Additionally, diets too high in protein can lead to what has been called “rabbit starvation”. Viljamur Stefansson, the Arctic Explorer, said the only time he had issues with the carnivore diet was when he didn’t get sufficient fat. 

“The groups that depend on blubber animals are the most fortunate in the hunting way of life, for they never suffer from fat-hunger. This trouble is worst, so far as North America is concerned, among those forest Indians who depend at times on rabbits, the leanest animal in the North, and who develop the extreme fat-hunger known as rabbit-starvation.”

Brains Need AA and DHA to Grow

Not only did our brains have an energy requirement to grow. The brain needs a concentrated source of preformed fatty acids. 

With the emergence of Homo Habilis, our brain growth accelerated and significantly exceeded that of Australopithecus. Australopithecus brain size had stayed constant for 2mya before the emergence of Homo Habilis.

What changed? Homo Habilis stopped playing Fortnite like their ancestors. Not really, but close. 

Homo Habilis created tools which allowed them to access more fat. But most importantly they discovered fatty acids that were necessary for their brain growth. 

In mammals, the polyunsaturated fatty acid content of the brain is virtually identical amongst various species. It is dominated by two main fatty acids: the Omega-3 DHA and the Omega-6 AA. 

Average polyunsaturated fatty composition of ethanolamine phosphoglycerols in brain

It appears that all mammalian brains require these two brain components, without which neuronal growth and function cannot occur. 

This posed a problem for Australopithecus who couldn’t access the requisite amounts of DHA and AA to grow. Our livers can convert the plant precursors of EPA (the plant polyunsaturated fatty acid) to DHA and AA, but this process is very inefficient and doesn’t happen in sufficient quantities (once again, notice that the plant nutrients are the lesser version of their animal counterparts). 

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According to Loren Cordain and Neil Mann, this limited availability of fatty acids is what prevented our brain growth:

“Hence, the limited  availability of these  two fatty acids from endogenous  metabolic synthesis may have represented the evolutionary ‘bottleneck’ impeding the encephalization process  in all herbivorous mammals.”

However, once we developed tools to access the brain and marrow, we hit the DHA and AA jackpot. The marrow provided a concentrated energy source and the brain provided the DHA and AA our brains needed to growth. Without the presence of these fatty acids, our brain growth and evolution would not have occurred. 

It was during this period (~1 million to 500,000 years ago) that a substantial part of our ancestors’ brain growth occurred .

Animal fat is essential for your brain. For growth and proper neuronal function. This is why DHA has been used to treat depressive disorders . 

And preformed DHA and AA are not present in plant products. Plant foods alone cannot support your brain. 

Because of the preformed fatty acids and high energy of animal products, all carnivores have a proportionally larger brain compared to their herbivore prey.

Do you want to be the predator or prey? 

Different animals' relative brain weight as percentage of total body weight

What Fatty Foods Were Available?

Early hominids needed energy, nutrients and fatty acids. The table below from Cordain and Mann shows the energy calories, fat, protein and fatty acid content of foods  available to early hominids. 

Comparison of energy density, protein content, and AA & DHA in food sources to early hominids

As you can see, no one food contains sufficient amounts of fatty acids, high energy density (kcal) and protein. The highest energy foods like marrow are devoid of DHA. The highest protein foods are devoid of fat and DHA. And the highest foods in DHA did not have sufficient energy. 

The only way to get these all in sufficient quantities is by consuming the entire animal, nose to tail. 

Homo Habilis was only approx 50 inches tall and did not have sophisticated weapons. It’s unlikely that they would have been able to kill the larger ruminants available at the time. 

But luckily for them (and us), other predators did the work. A field study of the carcasses in the Serengeti region of Africa shows that lions devoured these animals and left behind the skulls and marrow. 

“the marrow and head contents were the last items consumed and that defleshed marrowbones with intact marrow and defleshed heads with intact brains were the items most likely to be abandoned . Hence, head contents and defleshed marrowbones would have been the most frequently available body  parts to prehistoric scavengers, as they are today”

Early humans were not hunters, but scavengers for fat using the primitive tools they developed. 

The animals we scavenged were often old and rotten. Our stomachs had to adapt to the bacteria content and became more acidic.

Stomach acidity protects against pathogens. Thus a higher acidity often indicates a diet high in bacteria. The lower the pH, the higher the acidity. Humans have a stomach pH of 1.5, which indicates that our diets were likely high in scavenged food. 

Scavenged brain and marrow were the perfect foods to grow our brain. What were the lions thinking leaving them behind? Well, they weren’t thinking — because they didn’t eat the DHA and AA.

Human Evolution

Homo Habilis evolved into Homo Erectus and brain growth continued. Homo Erectus was also heavier and taller than its precursors. 

With their growing brain, they developed more sophisticated tools to compete with lions to kill the larger ruminants available. 

Anthropological evidence showed that they used hand axes to butcher larger animals . 

Brain growth of humans in evolution

As a result animals available to Homo Erectus to eat were substantially larger. 

“Archaeological evidence seems to associate H. erectus with large and medium-sized game (BSGA Elephant, >1000 kg), BSGB (Hippopotamus, rhinoceros approx. 1000 kg), and BSGC (Giant deer, red deer, boar, bovine, 80–250 kg)”

You read that correctly. Elephants were over 1000kg, over 2x the size of the biggest elephants that exist today. These were like sumo wrestler elephants. 

This walking gold mine was available, until around 400,000 year ago, when they went extinct. One hypothesis to their disappearance is that we got greedy and killed them all off. 

Different animals and their live weight, fat and protein percentages

Due to their size, we developed more sophisticated techniques to kill them off. Some of them are described below:

‘One entails hiding in the bush next to an elephant path, surprising it from the rear and cutting its tendons. Another practice is that of trapping by digging a round pit of some 2 m in diameter and 3 m in depth in the midst of the elephant path, while spears are placed at the bottom and the top is covered with branches . Another method entails scaring the elephant from behind against a barrier built of thick vines while forcing the animal to escape towards the barrier where it can be speared (:115).”

Disappearance of Elephants → Homo Sapiens

The extinction of these larger ruminants was a disaster. Some estimates suggest that over 60% of our calories were from these elephants. 

Humans easily could have gone extinct along with them. 

But instead, early humans adapted. What didn’t kill them literally made them stronger.

Instead of the larger ruminants, we started to go after smaller and faster animals. 

Smaller faster animals required more energy to kill, but we were already at our protein limit. The only way to increase our energy intake would be to find more animal fat. 

“The absence of elephants, weighing five times the weight of Hippopotami and more than eighty times the weight of Fallow deer (Kob in Table 3), from the diet would have meant that hunters had to hunt a much higher number of smaller animals to obtain the same amount of calories previously gained by having elephants on the menu.”

This was one of our first stoic acts. The obstacle is the way. The rewards were cosmic. 

Evolutionary Response

What happened as a result of the extinction? 

Humans shrank in weight to reduce their metabolic rate and they developed longer limbs. They became better equipped to chase animals and developed the Usain Bolt like capabilities that humans have today. 

Evolution selected for humans that were more sophisticated and could utilize more advanced techniques to capture and kill animals. 

Fat was tougher to come by and as a result early humans had to develop the ability to spot fatter animals amongst a herd. 

“Citing ethnographic sources, Brink (:42) writes about the American Indians hunters: “Not only did the hunters know the natural patterns the bison followed; they also learned how to spot fat animals in a herd. An experienced hunter would pick out the pronounced curves of the body and eye the sheen of the coat that indicated a fat animal”

Homo Erectus was getting the bulk of energy from fat and it became an obligatory food source. It became an essential food source for brain function and for energy. 

When the largest source of fat disappeared, Homo Erectus had to evolve to find a new source. 

And that evolution required more cooperation. Cooperation that created the social species that we are today — the cooperative hunting, division of labor, food sharing and offspring provisioning.

There’s an incredibly symbiotic relationship between Homo Sapiens, brain size and fat. 

Fat is sacred, and we would not be here today without it. 

The Carnivore Aurelius Way

Humans had to evolve or die. The stress catalyzed a response that led to an ultimately greater gain. 

We got complacent and comfortable with the unfettered supply of animal fat. And when the black swan extinction event happened, we became vulnerable. 

But instead of playing the victim card and wallowing in sorrow, humans evolved. They used the obstacle as fuel to get better. And holy shit the results were remarkable. 

They were literally living the Carnivore Aurelius way. 

Our remarkable cognitive capacity developed as a result. If this extinction — one of the worst events to ever happen to early humans — had never happened, we wouldn’t be here today.

There’s a massive lesson in that. 

Put yourself in stressful and uncomfortable situations. That is where you’ll see the most growth. And eat fat to fuel those efforts. 


Humans are carnivores and food is information. If you feed yourself what you have evolved to eat you will thrive. If you shock your body with new and processed sludge, your body will revolt.

The choice is yours. The carnivore diet will give you back control of your health.

We’ve talked about a lot here, and I really hope that you get a lot out of this article. It wasn’t easy for me to learn all this information – it took me years to learn about these things and improve my own health.

It doesn’t have to take that long for you. If you want to continue this journey and start improving your health, check out the getting started with the carnivore diet guide I prepared for you by clicking the button below.

Additionally, if you’re interested in learning more about the carnivore diet, join my Facebook group Carnivore Nation. I also post daily on Twitter.

It’s time to take back control.