Did Homo Sapiens scale its Brain by eating Brains?

Epistemic status: uncertain, but plausible

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 was once the apex predator among apex predators.

The Apex Predator.

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

all the way at the very top

To figure out what animals eat scientists do this thing called nitrogen isotope analysis.

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 paleolitic 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 hunter gatherers: 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.

The Big Brained Apex Predator

We have big brains. We have, comfortably, the largest brain-to-gut ratio among primates.

Big Brains; Small Gut. Is the entirely 100% correct way to summarize what human beings are in my opinion. But a smaller gut creates another problem. You now need food that gives you large amounts of energy and nutrients without requiring a gigantic fermentation chamber to extract them. So like, animal flesh.

Just to get your DRV of DHA from nuts or plants would require you to eat 270 grams of walnuts a day. Doable. But even a very plant-nut favored scientific establishment recommends you get your DHA mostly elsewhere. Note, algea supplements didn't exist back in our paleolithic days.

So you see, we were primates, that, unlike other primates, could hunt anything. We then also hunted everything including literal lions. With our small gut, we could have a big brain, but only if we actually ate more brains, because there's just not enough of the stuff we need to make our own brain in plants or nuts. So we did eat more brains than any other primate, and this then gave us the tissue to scale our brains. Of course this is a mere hypothesis of mine, but it's one I take seriously.

I'd be curious if anyone can find any other real material source of DHA to build our brains with on land that isn't brains. As far as I can tell, it's just brains.

For a significant part of our evolutionary history we were the big brained apex predator and we ate like the apex predator.

Then civilization happened and we started eating wheat or rice, our trophic levels have decreased from apex predator level now similar to that of a normal primate

And I believe this is why: our brains have been shrinking at an alarming rate.

In return for smaller brains we got more humans out of the same amount of land. More humans plus the demands of farming is what bootstrapped the need for institutions and bureaucracies and eventually civilization itself. However, the computational unit civilization 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.