An evolutionary history of the human brain, in 7 minutes | Lisa Feldman Barrett

Plato and Carl Sagan were wrong about the human brain, says a top neuroscientist.

Plato famously described the human psyche as two horses and a charioteer: one horse represented instincts, the other represented emotions, and the charioteer was the rational mind that controlled them. Astronomer Carl Sagan continued this idea of a three-layer "triune brain" in his 1977 book The Dragons of Eden.

But leading neuroscientist Lisa Feldman Barrett challenges this idea of the brain evolving in three layers, instead revealing a common brain plan shared by all mammals and vertebrates. The development of sensory systems led to the emergence of the brain, and hunting and predation may have initiated an arms race to become more efficient and powerful predators.

Despite advances in neuroscience and genetics, the question of why the brain evolved remains elusive. But Feldman Barrett's fascinating exploration of the brain's evolution offers insights into the most important functions of this complex organ, and invites us to think more deeply about the origins of our own intelligence.

Read the full video transcript: the-evolution-of-the-human-brain

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[coolbreeze]

For someone who has Myalgic Encephalomyelitis (chronic fatigue syndrome), there is an intense, first hand knowledge of metabolic efficiency and how it effects every second of our lives.

Everyone experiences it in different ways but from what I've experienced, it's like having difficulty doing 2+ things at once at the risk of burning out my internal "battery". Sitting up while eating and being able to hold a conversation is now impossible. Sitting up, which uses your muscles and balance systems is an action, coordinating your hands to bring the food to your mouth is another, digesting is another and being able to string words together to verbalize is another.

The brain takes up so much energy so the power needed for other parts of the body isn't there when trying to do things simultaneously. Digesting food then takes energy away from the brain so I need to lay down in silence. When I try to talk, it comes out gibberish like I'm having a stroke. Once I'm done digesting my food, my speech comes back.

Before getting sick, I didn't even think about how so many things in the body need to be coordinated at every moment to allow us to be functional.

It's truly a miracle how many reactions and mechanisms must work perfectly just for simple movements. This is something that should never be taken for granted!

[floepiejane]

I always thought it was just a metaphor. I never thought to think that some people took it seriously.

[MrFossilabgfyth]

The brain is a complex organ, I consider it a gift.
Yet most of the time, people tend not to use it well.

[Anonymous-yhol]

I've always learned it as "Reptilian Brain". "Lizard Brain" is something I've learned from media.

[arielsong]

As a young researcher, this channel is basically my lit review short cuts.

[terenzo]

"Lizard" is just shorthand for "primitive". I wouldn't worry about it too much or take it too seriously.

[ConnoisseurOfExistence]

She started by saying how energy expensive our brains are and finished with how important metabolic efficiency is...

[bubblybull]

That was a long teleologic answer, which is quite ironic since she denounces a scientifc reflex to turning to teologic answers…

[jhurley]

It’s not that “you don’t have enough energy”, it’s that you do not have sufficient “order”
to do the job!

[tameracikalin]

What is up with the annoying music overwhelming the speaker?

[treich]

Why did human brains evolve beyond the necessity for survival. when most organisms haven't?

[avonsternen]

Interesting insight by Plato regarding the function (regardless of the structure) of the human mind and brain.👍

[gmw]

Brains are receivers. The more complex, the more frequencies it can receive. But humans are trained to ignore most of them.

[thomassoliton]

Many primitive organisms have sensory organs (cells) that determine light, contact, temperature, pH, salinity, nutrients, etc. Even single cells (paramecium, euglena amoeba) have such sensors. The next step, like amphioxus and jellyfish, was a “nerve net” capable of taking that information and automatically directing movement toward or away from good or bad conditions, capturing prey, and feeding. The next step was forming memories. That is where “brains” began to evolve. Aplysia (sea slug) for example, “habituates” to repeated stimuli, a primitive adaptive response. But the reason we eat plants and not vice-versa is that we remember information and use it to PLAN responses rather than reflexively responding. The processing required to compare sensory input to memories and manipulate ideas to make plans requires tremendous connectivity between brain regions dedicated to different types of information, as well as a “central planner” communicating between most other regions to coordinate responses. Memory is the key because we cannot consider alternative responses without it.

[chem]

I think her explanations contain just as many simplifications as the "lizard brain" concept.
Good info, but we definitely have primitive functions running in the background. That's what people mean when they say "lizard brain".

[papermoonJanuarybloom]

Very interesting! Thank you for the explanations, they are all new knowledge for me.

[Michaelfrikkie]

Predatory behaviour seems to be almost as old as life itself - single-celled organisms prey on each other... This makes suspect the proposed "best guess" for brain development in this talk. At least it might indicate that the evolutionary "pressure" for brain development would then be much earlier in the evolutionary history.
The teleological "why things develop" studies are very important, but have to be tested/modelled to identify if pure mechanistic structural and dynamical probabilities allow any novelty to persist - structurally and dynamically proven to be an advantage in the sense that it has higher probabilities to reproduce and persist with only beneficial random modifications - Otherwise the existence of those structures cannot be ascribed to the actual mechanisms that caused it.
Are they doing those structural and dynamic probability analysis in their studies or are they just assuming higher probabilities because they observe the structure exist or existed, and they have a viable teleology or evolutionary pressure narrative? That is not a correct scientific approach and will lead to wrong conclusions about the underlying mechanisms that caused the evolution that is observed. Without that analysis, you will not be answering the question of why the probabilities are higher, because mechanistically and dynamically those probabilities might in fact be much lower from any previous ancestor in any possible environment.
It will cause the same kind of failure as the lizard brain hypothesis... it is dangerous to our own understanding and how we act on our understanding.

[MarcelinoDeseo]

basically the brain more likely evolved to efficiently coordinate the sense and motor functions of the body, minimizing energy loss and maximize chance of reproduction, even if the brain consumes most of the energy of the body.

[MindWorld]

The ability of the human brain
to store and recall memories is truly amazing!
Memories can evoke powerful emotions
and influence our
behavior.)

[poksnee]

But why did humans develop intelligence way beyond what is necessary to survive?