I'm going to make the claim that eating meat, and specifically DHA-rich meat, fish and most importantly the brains of land animals, is core to who and what we are as human beings. And because we have mostly stopped doing this in the amounts that are necessary, we are now, long-term, totally screwed.

I think we've all seen this chart:

At some point in evolution the brain to body ratio of some primate species diverged.

My claim is that. Although there will be genetic interrelated reasons for this, the tissue to scale our brains like this came, simply put, from eating the brains of other animals. It could not have come from any other places. There's simply not enough nuts with ALA to get enough DHA to sustainably make brains this big, and too many human tribes lived too far away from coastal areas to get their DHA from fish.

The human primate is quite special, whereas other primates eat mostly fruits and nuts and the like. The human primate is the apex predator among apex predators.

The apex predator.

How high on top of the food chain did we stand?

all the way at the very top baby

To figure out what animals eat scientists do this thing called nitrogen isotope analysis. Because I stopped paying to chemistroy and biology after high school, I too have no idea what this really means and can't be bothered to think about it. But it's probably something about decaying atoms something something, idk.

Scientists say that nitrogen isotopes give us a rough way of reconstructing trophic position and that as you move upward through a food chain, the heavier isotope nitrogen-15 becomes progressively enriched. Plants sit low. Herbivores eating those plants sit higher. Carnivores eating those herbivores sit higher still.

So if you take human bone collagen and compare it with the bones of animals from the same ecosystem, you can get a rough idea of where the humans were eating in the food chain. Neanderthals repeatedly show nitrogen-isotope values as high as, and sometimes higher than, the large carnivores living beside them. Analyses from places like Vindija, Marillac and Scladina put them right at the top of their ecosystems, with most of the protein represented in their collagen apparently coming from animal sources.

Upper Paleolithic Homo sapiens in Europe show the same basic pattern: very high trophic-level signatures, consistent with humans eating enormous amounts of animal food. Some mid-Upper Paleolithic modern humans had even higher trophic values because substantial amounts of their protein came from freshwater animals.

I actually visited hunter gather tribes a long time ago in africa. I do remember them eating brains (graphic warning, a homo sapiens eating the brain of another primate species) but I didn't think much of it back then. As once upon a time I had a need to fix my health, including brain and central nervous system inflammation. I now understand the deep wisdom behind this practice. Nothing cured my brain fog as well as extremely high amounts of salmon sashimi, fish oil supplements, vit B supplementation, high cholesterol, and desiccated beef brain supplements. Note, if I had just eaten brain, I would have gotten all of those + more in the same package. But it was a bit too gross for me.

If you ask, what is your favorite food. They will often say "the brain of a primate", they may also say honey. Primate flesh however seems the favorite type of meat of basically every tribe i've seen online. Which, makes sense doesn't it?

Notably, eating brain (and liver) was until quite recently very common. Einstein and Hilbert probably ate a ton of it.

So for a significant part of our evolutionary history, we were the apex predator, and we ate like the apex predator.

Then civilization happened and civilization discovered one of the greatest ecological hacks in human history: stop eating the herbivore and eat the herbivore's food directly: wheat, rice, maize, tubers. This is, from the perspective of producing as many humans as possible from a fixed amount of land absolute genius because every trophic step wastes energy. Plants capture sunlight. Herbivores eat plants and burn most of that energy staying alive. Humans eat the herbivores and lose another enormous fraction along the way.

And as a result: Our brains have been shrinking.

You do not get to massively increase the metabolic cost of one organ without paying for it somewhere else. If you want a brain that consumes an insane amount of energy without increasing total basal metabolism by the same amount, something else has to become cheaper. In our case that something was the gut. But a smaller gut creates another problem you can no longer live as efficiently on enormous quantities of bulky, difficult-to-digest food. So you need better food. Food that gives you large amounts of energy and nutrients without requiring a gigantic fermentation chamber to extract them. So like, animal flesh.

We took an animal that had spent hundreds of thousands of years occupying an unusually high trophic position, with an unusually large brain, an unusually small gut and access to extremely nutrient-dense animal tissues, and we reorganized its entire food system around cheap plant calories. In this way our collective intelligence could rise while the biological hardware running civilization deteriorates.

Before civilization there was meat.

Civilization replaced meat with calories and culture. But the computational unit it runs on is now steadily deteriorating. If we keep eating just like any other primate, we will eventually (tens of thousands of years) go back to having the brain size of any other primate.