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Updated: Mar 1

One of the most striking differences between us and chimpanzees and gorillas other than their strength is the size of their jaws. From the protruding mouth that holds all their teeth, to the massive jaw muscles for chewing. These adaptations are necessary as chimpanzees spend 1/3 of their day eating while gorillas spend 1/2 of their day eating. This is because their natural diet consists of mostly plant material with a low nutritional value. Humans, on the other hand, spend on average of a little over an hour eating. Our smaller jaw and face shows our specialization towards eating caloric and nutrient dense meat. Read on and I’ll show you the evidence.

Why did our brains shrink?

The smaller jaws in hominids coincide with the enlargement of their brains. This comparison is still useful even if you don’t believe in evolution, as these are adaptations of the hominids in the fossil record that are most similar to us. After about 2.5 million years ago, there was a pronounced increase in the size of the brains of hominids. That was the start of an ice age when plants were less available, and also when the we find the first evidence of tool use with Homo Habilis. These tools were first used for scavenging and breaking open the bones and skulls of prey left behind by predators, and later, as meat intake increased, for hunting.

There is a significant increase in brain size as meat consumption increased along with evidence of Homo Erectus hunting in groups. We know this is from an increase in meat consumption because there was no evidence of cooking until later on. This trend continues with Homo Neanderthals and finally Homo Sapiens, like us. But if you look at the zoomed in area at the end of the graph you can see a sudden decrease in brain size. Why did their brains shrink? Well, that is the start of the agriculture revolution and the reintroduction of plants as the majority of our diet.

The agriculture revolutions marks a massive decrease in diet quality and nutrient availability. As a result, we can see a sudden and significant decrease in brain size, stature, dental health, and wound healing. Animal products have the advantage of being nutrient dense, easily digestible, and bioavailable. There are no anti-nutrients to hinder absorption and the nutrients are in a readily /available form that don’t need to be transformed before it’s used, unlike plant foods.

As we can see from other hominids, humans naturally eat a significant portion of their diet as meat and other animal products. More evidence for this diet pattern comes from the Nitrogen isotopes found in bones. Herbivores have a level of stable Nitrogen isotopes (σ15N) from the plants they eat and carnivores have a much higher level because they eat the herbivores with all their σ15N. It’s what’s referred to as bioaccumulation. For example, look at the σ15N of the arctic fox during the pre-agriculture period. It is much higher than the herbivores like wild horses, but all 5 groups of Homo Sapiens were even higher. That is because humans were hyper carnivores. We ate the herbivores and the carnivores and got all their σ15N.

On our farm, we are trying to learn lessons from nature to improve how we manage our farm. We are integrating our farm animals back into the environment, and managing our farm more like a holistic ecosystem. Our pastured turkeys that follow our herd of grass fed beef mimic the birds that would follow the massive herds of bison that roamed North America. Our animals thrive on their natural diet, just like we need to eat our natural diet to thrive. Do you want to eat more of the food that made us human?

Sander van Stee

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