Your Brain on Meat

I think the best place to begin this series on Brain Food is the beginning – a look at the backdrop of the human brain. So let’s rewind the clock and see how the brain changed from that of our early ancestors to the modern Homo Sapien brain. This is the journey of your brain on meat.

Part I: Your Brain on Meat

• Section 1: Your Brain on Meat (this post – below)
• Section 2: The Brain-Body Paradox
• Section 3: Meat the Brain that Became Sapiens
• Section 4: Evidence for a Meat-Based Diet

Part II: Your Brain on Plants (coming soon)

Part III: Brain – Body Connection (coming soon)

Your Brain on Meat – Building the Brain

If we could turn back the clock about 3 million years, we’d find ourselves in an African forest. The weather would be warm. And we’d share the woodlands, riverines, and trees with other hominids – the great apes including orangutans, gorillas, and chimpanzees.

We might even see Lucy.

She was a Southern Ape, an australopithecine, who would be clumsily walking on two legs, munching on leaves and rummaging for seeds, roots, and fruits. Like the other hominids she was a herbivore and one of the closest relatives to the earliest humans. However, unlike early humans, her brain was much smaller, about 300-400cc. (r)

Our Earliest Ancestors’ Diet

Our early ancestors like Lucy ate a plant-based diet. And they spent most of the day doing just that – chewing through leaves and plants. They had very large guts (cecums) which housed a massive amount of bacteria that could converted this fiber to fat.

So although they ate a plant-based diet, they were fueled by fat.

A Fat, Plant-Based Diet

Gorillas are similar to Lucy.

A gorilla eats leaves and this activity take up most of their day.

Leaves are about 60% protein and 40% carbohydrate (with just a miniscule amount of fat < 5%).

But thanks to their large guts they can take all that fiber, which makes up about 75% of the leaves’ dry weight, and they can ferment it into short-chain fatty acids (SCFAs).

So, in reality, the gorilla eats a diet that is about 20% protein, 10% carbohydrate, and 70% fat – nearly all of which is saturated fat.

Our ancestors’ specialized guts wouldn’t have allowed them to eat much meat. If they did their large colons would be at risk of twisting causing immense pain and could even be fatal.

Your Brain on Meat: Adapt or Die

The fossil record shows an astonishing change about 2.5 million years ago. Humans diverged from their hominid ancestors. The distinguishing feature – the brain – began to explode in size.

Climate Change; Diet Divergence

This divergence coincided with another change. The earth began to cool.

Forest and waterways turned into arid savannah.

The series of Ice Ages began and continued up until about 12,000 years ago. The cold temperatures dried up the planet as freshwater was locked up in ice caps. (r)

Rains became more scarce. Luxuriant plant growth and rainforests turned into grasslands and tundra. Even places close to the equator had climate similar to that of Northern Canada today.

The backdrop of human evolution is one of long cold winters and short cool summers on African savannas populated with grazing animals.

Climate Crossroad

This climate change put our hominid ancestors at a crossroad.

As leaves, fruits, and flowers became increasingly scarce, it took more time and energy to venture across ever-spreading grasslands to find food.

The crossroad our early ancestors faced was to either continuing trying to subsist and compete for plant-based food that was disappearing or venture out and incorporate new sources of food. What the barren grasslands lost in vegetable life it gained in animal life. Meat was abundant.

We stood at a crossroad: adapt or die.

Lucy and the australopithecines chose to stick with plants and became extinct. Humans decided to do what we’ve become known for – we adapted, we ventured out, we took a risk. We started incorporating more and more meat into our diets. (r, r)

Undoubtedly, meat started off as a supplement to the plant-based diet of our ancestors. But as the weather and environment continued to change, so did our diet, and so did our evolutionary adaptations. (r)

Your Brain on Meat: A New Kind of Fat

With this divergence in diet came different nutrients.

Animal fat is different than the fats derived from plants.

Animal fat provides a ready-made source of long-chain fatty acids, including pre-made 20 and 22 carbon chain fatty acids (AA, DTA, EPA, DHA) all of which are essential for brain development. All of which are found only in animal foods.

The longest chain in vegetable oils – linoleic acid which is an omega-6 and alpha-linolenic acid which is an omega-3 are 18 carbon fatty acids. Humans, like all mammals, can chain elongate by desaturating these 18 carbon fatty acids to produce the longer 20 and 22 chain fatty acids – but we are extremely inefficient at doing this.

The conversion of 18 carbon fatty acids into the 20 and 22 carbon fatty acids would have been impossible to fuel the brains exponential growth. It’s far too inefficient.

But by eating preformed 20 and 22 carbon fatty acids via eating animals, humans were able to give the brain directly what it needed, instead of trying to endogenously synthesizing these fats from plant material. (r, r, r)

DHA and Brain Size

The importance of these animal-based fats on brain growth are highlighted in a recent randomized controlled trial.

This study showed that pregnant women given DHA supplementation had children with larger total brain volumes, more gray matter, as well as a larger corpus callosum and cortical volumes compared to the placebo group. (r)

Your Brain on Meat: The Loop

When we look back at the building of the human brain, we see a feedback loop that shaped our future.

Colder climate led to more meat consumption which led to bigger brains as natural selection favored the advantages associated with coordination and communication that facilitated successful scavenging.

This was a cycle that reinforced itself. A cycle that forced ever-increasing meat consumption to build an ever-growing brain, which required ever-more energy.

Handyman

This cycle started with Homo habilis, one of the earliest human species. He had a brain much larger (650cc) than Lucy’s. (r)

He was known as “handyman” because he butchered and skinned animals with stone tools.

Handyman survived for hundreds of thousands of years.

Working Man

Successor species like Homo Ergaster, “Working Man,” and Homo Erectus (1.5-1.8 million years ago) look closer to modern humans. (r)

By this time animals like reindeer, bears, rhinos, and mammoths had become the prominent food sources.

And as the feedback loop continued, the brain continued to grow, to about twice the size of Handyman’s.

In addition, Ergaster and Erectus were taller, less hairy, and used more extravagant tools like bone-basers and bi-faced hand axes to hunt in coordinated scavenging operations. (r)

With later species, like the Neanderthals, hunting was a fulltime job. And by this time the brain had expanded to an enormous 1500cc, 4X the size of our early ancestors – even bigger than our brains today. (r)

Sapiens

With sapiens, about 200,000 years ago, we saw the next leap in hunting technology and ingenuity. Along with their spears, daggers, and fish hooks, lies the remains of the bones of wildebeest, giant cape buffalo, and the large, fierce animals of the day demonstrating the skill and cooperation of a human specie that was big-game hunters. (r)

Communication and cooperation, ingenuity and invention, are hallmarks of the human brain, features that catapulted humans to the top of the food chain.

Your Brain on Meat – Meat Heads

Meat was the fork that diverged humans from our hominid ancestors. (r)

From habilis to erectus to modern sapiens, meat gradually became the staple food of humans. (r)

In fact, isotope studies of fossils reveal a human diet about 50,000 years ago as indistinguishable from a carnivore diet. (r, r) Chemical analysis of tooth enamel reveals the same thing. (r)

As we’ll see in the coming sections, this meat not only built our brains, but it changed our bodies. (r) Our huge brains became our biggest weapon and biggest liability. It’s the distinguishing feature that makes humans human. We built these magnificent brains over millions of years.

Recently we’ve started tearing them back down at an alarming rate. We’ll be diving into this in Part II – Your Brain on Plants.

In the next section of Your Brain on Meat – “The Brain-Body Paradox” we’ll see how the brain changed the body, and the great sacrifices made to support the brain.

In the meantime, The Health Dangers of a Plant-Based Diet, is a great precursor to Part II in the Brain Food Series: “Your Brain on Plants” (coming soon).