SELF | Deep Dives
Exploring how to develop our SELF through health, wealth, and connection.
SELF | Deep Dives
Brains Beat Brawn: Why Dinosaurs Lost to Mammals | Ep. 03
We explore the evolution of movement in the animal kingdom through the lens of Nikolai Bernstein's groundbreaking work, tracing the journey from single-celled organisms to modern mammals. This fascinating evolutionary story reveals how movement capabilities evolved through natural selection's relentless pressure.
• Bernstein's perspective that understanding nature requires knowing its history and evolution
• Using a 1:50 million scale to comprehend biological time (100 years equals 1 minute)
• Early movement evolving from chemical signals to electrical transmission
• The revolutionary development of striated muscle with thousands of times more power
• The evolution of specialized body structures like limbs and centralized nervous systems
• How sensory feedback loops enabled increasingly complex movement patterns
• Arthropods' exoskeletons offering protection but limiting adaptability and intelligence
• Reptiles dominating for millions of years before being outcompeted by mammals
• The critical development of the cortex and pyramidal motor system in mammals
• Movement quality evolving from programmed instincts to adaptable, improvisational abilities
Think about your own movement capabilities and how they reflect this incredible evolutionary journey that spans billions of years. How might this competition continue to shape both natural life and our technology going forward?
All right, welcome to another deep dive. You know why you're here, right? You love knowledge, you're curious, but you also wanna get to the good stuff. That's what we're all about here. Today's deep dive is a fascinating one. We're gonna be looking at how movement evolved in the animal kingdom, and our main source is gonna be the work of a guy named Nikolai Bernstein. You might not have heard of him, but he had some really interesting ideas, like really foundational stuff about how life went from well, not moving at all to the amazing diversity of motion we see today, and we're going to see how this all happened because of what Bernstein called the great competition of life. You know that constant pressure to adapt or die. So get ready, because this one's going to make you think.
Speaker 2:Well, bernstein starts off with this idea that really sets the stage for everything else. Yeah, to understand something in nature, you've got to understand its history.
Speaker 1:Yeah, makes sense Like if you read a poem, right?
Speaker 2:Right. To really get it, it helps to know something about the poet's life. Or if you're trying to judge someone's actions, well, you kind of need their backstory. Yeah, and Bernstein says it's the same for the natural world, and this is especially true for something as dynamic as movement.
Speaker 1:And it's not just about looking at individual animals, right Like even the universe itself, which seems pretty stable, is always changing.
Speaker 2:Yeah, always changing. Stars are being born, stars are dying.
Speaker 1:But when we look at living things, that change is even more, I don't know, intense.
Speaker 2:Absolutely the world of living organisms. It's like this constantly active arena, this what Bernstein calls a merciless struggle for life.
Speaker 1:So only those with the right stuff make it.
Speaker 2:Right, only the ones with the right adaptations, the lucky ones who happen to develop the right inventions. They're the ones who survive and pass on those traits, and that's that's really the engine behind how movement developed.
Speaker 1:Like these new ways of moving these. I guess you could call them technological revolutions in biology. They gave some animals a real advantage, right?
Speaker 2:You got it. They became more flexible in how they lived, better at coordinating complex tasks and, in the end, more resourceful in dealing with their environment.
Speaker 1:It's like a biological arms race, I guess. Yeah, better movement means you're more likely to survive.
Speaker 2:Exactly Now, when we're trying to understand something that happened over billions of years, it can be tough to figure out where to even start. We don't exactly have video footage right.
Speaker 1:Right, so how do we do it?
Speaker 2:We have two main sources of information. We have the fossil record, which is the actual preserved remains of ancient life. You find them in layers of rock and they can tell us well what these creatures look like. And how they moved and sometimes even how they moved.
Speaker 1:Yeah, but fossils, they don't always tell the whole story, do they? I mean, I'm guessing, those softer tissues and organs. They don't last very long, especially over millions of years.
Speaker 2:That's the problem, that's the limitation. So that's where our second source comes in, and that is comparative anatomy and physiology.
Speaker 1:So by looking at how living animals are put together and how their bodies work.
Speaker 2:Yeah, we compare them and by looking at the similarities and differences we can kind of infer how they're related.
Speaker 1:And how their ancestors might have been like.
Speaker 2:Exactly, and what's really neat is that when we do find fossils that kind of overlap with what we're predicting it almost always matches up.
Speaker 1:It's like having two pieces of a puzzle that fit perfectly. It strengthens the evidence.
Speaker 2:Oh yeah, the evidence.
Speaker 1:Oh yeah, now to even try to grasp this vastness of time that we're talking about billions of years bernstein uses this really interesting analogy oh yeah, it's a good one. It kind of helped me wrap my head around it.
Speaker 2:It's a 1 to 50 million scale, right, right. So think about it this way if you take a hundred years and compress it into just one minute, a hundred years is now one minute okay your entire life would only be what? Maybe like 40 to 45 seconds, wow. And then suddenly, earth isn't this ancient, you know, infinitely old thing.
Speaker 1:It's more relatable, right, yeah?
Speaker 2:Much more. It's only been around for like the equivalent of 40 years 40 years. Okay, and life itself has only been around for about half that time 20 years and vertebrates our own branch of the animal kingdom. They only show up like 10 years ago on this scale In mammals. They don't even show up until like two to three years ago. Wow.
Speaker 1:And humans.
Speaker 2:Humans are less than a week old on this scale.
Speaker 1:Oh wow, that's crazy.
Speaker 2:Think about it this way All of recorded human history, everything we've written down, that's just the last hour on this scale.
Speaker 1:And all of modern science.
Speaker 2:Just the last few minutes.
Speaker 1:Really puts things into perspective, huh. And in all that time, life's been branching out and becoming more and more complex, and Bernstein gives us a good overview of the major steps along the way.
Speaker 2:Yeah, he does. In table one. He calls it the ladder of life. It starts with those single-celled organisms, the protozoa, and goes all the way up to us, the vertebrates.
Speaker 1:And he points out all the big innovations along the way.
Speaker 2:The big leaps yeah.
Speaker 1:Like developing a complete digestive system, which is basically a tube with a mouth at one end and, well, an exit at the other.
Speaker 2:Exactly Not like those jellyfish with their single opening for everything.
Speaker 1:Yeah, that's a big step up. And then there's body segmentation. Yeah, you know, like in worms.
Speaker 2:Right right, which allows for more flexible and coordinated movement.
Speaker 1:And then, of course, the arrival of skeletons and limbs. That's a game changer.
Speaker 2:Absolutely, but maybe even more important is the development of a central nervous system.
Speaker 1:A brain.
Speaker 2:A brain, yeah.
Speaker 1:Right. That's huge for coordinating all those complex actions. So let's go back to the very beginning. How did movement even get started?
Speaker 2:Well, picture the early oceans. They were like this rich soup of molecules, constantly bumping into each other.
Speaker 1:And in all that chaos, something incredible happened.
Speaker 2:Right. One of those random collisions led to the formation of a very special molecule, one that could actually make copies of itself.
Speaker 1:The very first live particle, as Bernstein calls it.
Speaker 2:Exactly, and that's the start of life as we know it that drive to self-preserve and multiply.
Speaker 1:So we start with single-celled organisms and over time they evolve into multicellular ones.
Speaker 2:And with that comes specialization, different cells taking on different roles.
Speaker 1:Like a division of labor.
Speaker 2:Yeah, exactly. Some cells on the surface. They become sensitive to the environment, excitable. Others, deeper inside, they specialize in contraction. That's where we get our muscle cells from.
Speaker 1:So those early movements were probably pretty random. Right, Just twitches.
Speaker 2:Probably. But even those random twitches, even those could be an advantage compared to being completely still.
Speaker 1:I guess if you're moving around you're more likely to bump into some food or avoid a predator.
Speaker 2:Exactly, and that's what drives natural selection.
Speaker 1:So then what? How do these early organisms get better at moving?
Speaker 2:Well, they developed chemical messengers. These are substances released by the sensitive cells, the ones on the surface.
Speaker 1:In response to the environment, and then those messengers can trigger contractions in the muscle cells.
Speaker 2:You got it. It's the first form of communication within a living thing. And these chemical signals, they're ancient.
Speaker 1:Really ancient.
Speaker 2:Like Bernstein says, every time you consciously move a muscle, you're using a mechanism that's been around for half a billion years.
Speaker 1:Wow. So over time these chemical signals get more refined, but then something truly revolutionary happens.
Speaker 2:Bioelectricity, the beginning of the nervous system.
Speaker 1:In a way. Yeah, it's like this Every chemical reaction has an electrical side to it. When a sensory cell is activated or when it releases those chemical messengers, there are tiny electrical changes happening, and what happened is that some muscle cells evolved to become sensitive to these tiny electrical signals and that was huge.
Speaker 2:Because, Electricity is so much faster than chemicals.
Speaker 1:Right.
Speaker 2:Think about a reflex, like when you touch something hot.
Speaker 1:Yeah, it's instantaneous.
Speaker 2:So this electrical signaling, it starts to take over. Brunstein describes it like a professor and his shadow.
Speaker 1:Okay, okay.
Speaker 2:The shadow is electrical excitability. At first it just follows the professor, which is the chemical signaling, but then it becomes independent, even more important. So these electrical signals, they're moving fast, but they're still spreading out kind of randomly. So what happens next is the development of nerve fibers.
Speaker 1:Specialized cells that can carry those electrical signals more efficiently.
Speaker 2:Exactly, and they start forming the first neural networks. At this point it's pretty basic, just direct connections between sensory and muscle cells.
Speaker 1:But it's a start right.
Speaker 2:Oh, it's a huge start. This is the foundation of the nervous system.
Speaker 1:So we've got basic movement, a simple communication system. What's the next big step?
Speaker 2:Well, the next big step is the evolution of elongated animals, what Bernstein calls sausage-like. Think of early worms and mollusks.
Speaker 1:Okay, so they have a clear front and back, a head and a tail.
Speaker 2:Exactly. And that front end, the head, becomes really important, because that's the part that's exploring the environment. It encounters food or danger first, and the body just naturally follows.
Speaker 1:Makes sense.
Speaker 2:So the head is leading the way, and because of that the senses start to concentrate at the head.
Speaker 1:So we have what's called contact sensitivity, right.
Speaker 2:Exactly Touch, taste, temperature and detecting chemicals in the water. But something even more revolutionary happens the development of telereceptors.
Speaker 1:Senses that can perceive things at a distance.
Speaker 2:Yes, like smell, hearing and vision, bernstein actually traces a direct path from those early contact senses to these long range senses, like taste evolved into smell, touch into hearing.
Speaker 1:And sensitivity to temperature and division.
Speaker 2:Exactly, and these long range senses, they completely changed the game. Because, because now animals could sense things far away, not just what they were touching.
Speaker 1:So they could find food from a distance or avoid danger.
Speaker 2:Exactly. They could anticipate and react, which gave them a huge survival advantage.
Speaker 1:And this changed how they moved right.
Speaker 2:Absolutely those localized, segmental movements, like a worm just wiggling a part of its body, those weren't enough anymore.
Speaker 1:Because the food or the danger might be far away.
Speaker 2:Exactly so. They needed to move their whole body locomotion.
Speaker 1:And to coordinate that kind of movement you need a more complex nervous system.
Speaker 2:And that's where the brain comes in. It's located at the front, where all those new senses are. The captain's bridge, bernstein calls it.
Speaker 1:And this brain has to coordinate all the muscles in the body, make sure they're working together to move in a unified way.
Speaker 2:And there's more being able to sense things from afar. It gives you time to plan. An animal can hide, prepare an ambush.
Speaker 1:It needs some kind of memory.
Speaker 2:Exactly, and that drives the development of intelligence and dexterity, all of which require a more developed brain.
Speaker 1:So this seemingly simple change, developing a head and a brain, it has huge consequences.
Speaker 2:It's a cascade of evolutionary changes, but the pressure keeps building right. The competition for survival gets even tougher.
Speaker 1:And those soft-bodied creatures. They're pretty vulnerable.
Speaker 2:Right. So we see two main strategies emerge. Some animals go the route of passive defense, like developing shells, like mollusks.
Speaker 1:But the other strategy, the more active approach, is the one that really takes off.
Speaker 2:And this is where we see a huge leap forward the emergence of striated muscle.
Speaker 1:Or muscular aniso elements, as Bernstein calls them.
Speaker 2:Yeah, he loves his terminology, but this was a revolutionary development. Because, Because striated muscle is what allows for quick, powerful movements, like a bird flapping its wings.
Speaker 1:It's so much more powerful than smooth muscle.
Speaker 2:Way more powerful. For the same amount of tissue, it can generate thousands of times more power.
Speaker 1:It's almost like evolution stumbled onto this amazing design.
Speaker 2:It's a remarkable development and it's adopted so quickly, even though it had some drawbacks at first.
Speaker 1:Drawbacks Like what?
Speaker 2:Well, one problem is that the contraction of a single striated muscle fiber is very jerky, almost explosive. It could damage delicate structures.
Speaker 1:So evolution had to come up with a way to smooth things out.
Speaker 2:Exactly, and the solution was to incorporate tiny elastic elements within the muscle fibers. Bernstein calls them isoelements. They're like miniature shock absorbers.
Speaker 1:They stretch during contraction and release the energy gradually.
Speaker 2:Yeah, exactly, and that's actually what gives striated muscle its striped appearance.
Speaker 1:Interesting, but that wasn't the only problem, was it?
Speaker 2:No, it wasn't. Another issue was that striated muscles couldn't sustain a contraction for very long.
Speaker 1:They were good for short bursts.
Speaker 2:Right. So the nervous system had to evolve a new trick Tetanus.
Speaker 1:Which is.
Speaker 2:It's a rapid sequence of signals sent to the muscle. It's like a machine gun firing.
Speaker 1:So instead of one big contraction, it's a series of small ones that blend together.
Speaker 2:Exactly, and that creates a sustained contraction.
Speaker 1:Clever, but that must be pretty inefficient, energy wise.
Speaker 2:It is. Each of those little contractions requires energy, even if the muscle isn't doing much work.
Speaker 1:So just holding a weight still takes a lot of energy.
Speaker 2:Yeah, and then there's the problem of controlling the force of contraction.
Speaker 1:How do you make a muscle contract? Just a little bit or a lot?
Speaker 2:Well, a single striated muscle fiber, it's all or nothing Like flipping a switch.
Speaker 1:Either it contracts fully or it doesn't.
Speaker 2:Right. So to get finer control, the nervous system developed motor units, which are Groups of muscle fibers controlled by a single nerve.
Speaker 1:So by activating different numbers of motor units, you can control the overall force.
Speaker 2:Exactly, it's like having a dimmer switch instead of just a non-off switch. It sounds like striated muscle was this powerful new tool, but it took a while to refine it. Like Bernstein says, it's like getting a powerful passenger car when what you really need is a thresher.
Speaker 1:Right, right. So let's go back to the arthropods. They went the route of the external skeleton. What happened to them of the external skeleton? What happened to them?
Speaker 2:Well, that exoskeleton. It had its advantages stability, protection, and they didn't need to use muscles to maintain their posture.
Speaker 1:Sounds pretty efficient. So what was the problem?
Speaker 2:The problem was that it limited their flexibility and adaptability. They became very reliant on instincts.
Speaker 1:Instincts.
Speaker 2:Yeah, complex pre-programmed behaviors and those instincts work great in stable environments like a termite mound or a beehive.
Speaker 1:Where everything is predictable.
Speaker 2:Exactly, but if something unexpected happens, they're in trouble. Bernstein gives some great examples. Like what? Like those termites that get totally confused if you change their environment even a little bit.
Speaker 1:Right.
Speaker 2:Or a beetle that can't flip itself back over if it gets stuck on its back. They lack dexterity.
Speaker 1:They can't solve new problems, they can't learn and adapt.
Speaker 2:Right. So while some arthropods are incredibly quick, that's not the same as being resourceful, and their reliance on that shell it kind of blocked them from developing real intelligence.
Speaker 1:So they hit an evolutionary dead end.
Speaker 2:In a way, yeah, they found a successful strategy, but it had limitations.
Speaker 1:Okay, so let's move on to the vertebrates. They took a different path.
Speaker 2:They did, they went all in on the neokinetic system striated muscles. A centralized nervous system and a brain, and they really took advantage of that brain, didn't they Big time. Over time, the brain, especially the motor cortex, becomes the dominant force. It even starts to influence basic bodily functions.
Speaker 1:So if we look at vertebrate evolution, we see this progression through different classes.
Speaker 2:Right From fish to amphibians, to reptiles and then to birds and mammals.
Speaker 1:And the evolution of warm-bloodedness in birds and mammals. That was a big deal right.
Speaker 2:Huge. It sped up everything Nerves, muscles, everything worked faster.
Speaker 1:Now, one of the key innovations Bernstein talks about is sensory corrections. What's that all about?
Speaker 2:It's basically a feedback loop. As you're moving, your senses are constantly sending information to the brain.
Speaker 1:Like, hey, this is what's happening.
Speaker 2:Right and the brain compares that information to the plan for the movement and if there's a difference, it makes adjustments Exactly, and this allows for incredibly fine control.
Speaker 1:Which wasn't really necessary for those simpler animals.
Speaker 2:Right, their movements were mostly just reactions to immediate sensations, but for more complex movements you need this constant feedback.
Speaker 1:So, instead of sensations triggering movements, it's movements guided by sensations.
Speaker 2:You got it. And this need for sensory corrections. It drives further brain development, especially the sensory areas.
Speaker 1:And another key innovation is the development of limbs.
Speaker 2:Limbs yeah, those things we walk with. They evolved from the paired fins of fish.
Speaker 1:Like the frog it starts as a tadpole with fins and then develops legs.
Speaker 2:A perfect example and the development of limbs. It kind of bypassed the older segmented structure of the body.
Speaker 1:Which meant that they were controlled differently.
Speaker 2:Exactly, and this, along with the need for more complex locomotion, led to the centralization of the nervous system, the development of the brain as we know it.
Speaker 1:So vertebrate movement keeps getting more complex, but it's not random, right?
Speaker 2:No, it's driven by that constant pressure to survive the competition. Animals with greater force, speed, accuracy, they have the advantage.
Speaker 1:And the environment plays a role too, right.
Speaker 2:Absolutely. Moving on land is a lot more challenging than moving through water.
Speaker 1:You got to deal with obstacles, uneven terrain, so you need a wider range of skills.
Speaker 2:Exactly, and this need for dexterity. It pushes the development of the brain cortex even further.
Speaker 1:That's the part of the brain that deals with learning and problem solving.
Speaker 2:And intelligence. So now we get to the reptiles. They had a pretty good run, didn't they?
Speaker 1:Dominating the planet for millions of years.
Speaker 2:Yeah, During the Triassic and Jurassic periods they were the top dogs and they got huge, like really huge they had some advantages right Tough scales for protection and they developed a brain region called the striatum which helped with movement.
Speaker 1:And they even had the beginnings of a cortex. It's important to note that the cortex didn't just appear overnight. It was a gradual process. It started small and simple and gradually got bigger and more complex.
Speaker 2:Gradual process it started small and simple and gradually got bigger and more complex. Exactly and reptiles. They were also capable of a wider range of movements than fish.
Speaker 1:They could run, some could fly, they could swim, they could jump and they could even control and inhibit their movements to some degree.
Speaker 2:Right, but their reign eventually came to an end.
Speaker 1:What happened?
Speaker 2:Well, for one thing, their size became a liability.
Speaker 1:I thought size was an advantage.
Speaker 2:It was at first, but they were cold-blooded, remember.
Speaker 1:So their nerve impulses were slower.
Speaker 2:Much slower. All right, bernstein gives this example of calculating the reaction time of a giant reptile after being bitten. Yeah, and it's so slow that a faster predator could do a lot of damage before the reptile could even react. And their brains were also relatively small for their body size.
Speaker 1:Most of their head was taken up by their jaws and stuff.
Speaker 2:Exactly so. A lot of their movements were probably controlled by the spinal cord, not the brain.
Speaker 1:Which limited the quality of their movement.
Speaker 2:Right. And then there's the fact that most reptiles just lay eggs and don't take care of their young.
Speaker 1:So each generation had to learn everything from scratch.
Speaker 2:Exactly. They didn't have the benefit of parental guidance, so they were out-competed by the mammals.
Speaker 1:The mammals were smaller, faster, warmer and smarter.
Speaker 2:Exactly Now, before the mammals, there were the birds.
Speaker 1:And birds are amazing movers too, right.
Speaker 2:Oh yeah, they really represent the peak development of the striatum and the cerebellum, which is important for balance.
Speaker 1:Especially for flying.
Speaker 2:Right. So they have this complex extrapyramidal motor system, but it still has a bit of a delay built in.
Speaker 1:Because the signals have to go through multiple steps.
Speaker 2:But it wasn't a big deal for birds because they were small and warm-blooded and they have incredible senses and a wide range of movements.
Speaker 1:Running flying climbing.
Speaker 2:And they can even regulate and inhibit their movements pretty well, but they're still limited by their instincts.
Speaker 1:Even though those instincts can be very complex, like building nests and migrating.
Speaker 2:Right, they seem intelligent, but they're inflexible If something unexpected happens, they don't know what to do.
Speaker 1:They can't learn new things as easily as mammals.
Speaker 2:Right. But birds did develop family life and parental care, which probably helped them learn new movements, and they even have some expressive sounds and dances.
Speaker 1:They were getting close to that next level.
Speaker 2:They were, but they lacked that crucial ingredient a big, powerful cortex.
Speaker 1:And that brings us to the mammals and the pyramidal motor system.
Speaker 2:Which Bernstein says devoured the older extrapyramidal system.
Speaker 1:What does he mean by that?
Speaker 2:He means that the cortex became the dominant force in controlling movement. Even those early mammals had a more developed cortex than birds or reptiles and the older parts of the brain, the striatum and cerebellum. They became less important.
Speaker 1:So the cortex took over.
Speaker 2:In a way, yeah, and it developed connections to all the sensory organs.
Speaker 1:So it had all the information it needed to make decisions about movement.
Speaker 2:Exactly. And then there's the pyramidal motor system itself.
Speaker 1:What's so special about that?
Speaker 2:It's a direct connection from the cortex to the spinal cord. It bypasses all those intermediate steps in the older system.
Speaker 1:So it's faster and more direct.
Speaker 2:Exactly, and that's where the term extrapyramidal comes from.
Speaker 1:Because it's everything outside of this new pyramidal tract.
Speaker 2:Right. And this new system? It allows for a whole new level of control. Think of precise, powerful movements like aiming, grasping, throwing.
Speaker 1:These are the building blocks for complex actions like using tools, so mammal movements become less stereotyped and more adaptable.
Speaker 2:Right Bernstein compares it to musical improvisation.
Speaker 1:Instead of just playing a memorized piece.
Speaker 2:Exactly, and mammals are also much better at learning new skills.
Speaker 1:They're more trainable.
Speaker 2:And they have more complex social behaviors thanks to family life and parental care.
Speaker 1:And their vocalizations become more meaningful, almost like words.
Speaker 2:And they develop facial expressions which you don't really see in birds, and even the quality of their movement changes.
Speaker 1:Wow Sal.
Speaker 2:It becomes more elastic, more springy. They're rarely truly still.
Speaker 1:Even at rest there's this subtle movement.
Speaker 2:It's a different kind of control, and Bernstein concludes that this is why the reptiles declined.
Speaker 1:Because they lacked a big, powerful cortex.
Speaker 2:Exactly the mammals, with their new brain power and their new motor system. They were simply more adaptable, more capable and, on that compressed timeline, their rise was incredibly fast.
Speaker 1:And then, even more recently, humans come along.
Speaker 2:And we develop writing which leads to recorded history.
Speaker 1:And then the Renaissance and the scientific revolution.
Speaker 2:And yet our understanding of the brain and the nervous system. It's still in its infancy. There's so much more to discover.
Speaker 1:So this deep dive into Bernstein's work, it's really shown us this amazing story of how movement evolved.
Speaker 2:Driven by that constant pressure to survive and adapt.
Speaker 1:And the key takeaways.
Speaker 2:The interplay between structure and function.
Speaker 1:How, the way something is built, affects what it can do.
Speaker 2:And the power of even small evolutionary changes.
Speaker 1:And the huge impact of the brain.
Speaker 2:The brain is the key. It's what allows for all this complexity and adaptability.
Speaker 1:So by understanding this evolutionary journey, we can appreciate the incredible complexity of movement in all living things.
Speaker 2:Including ourselves.
Speaker 1:It's really mind-blowing.
Speaker 2:It is, and it makes you wonder how is this competition still shaping us today, not just in the natural world, but in our technology too?
Speaker 1:What new revolutions are waiting for us?
Speaker 2:Think about that, think about the legacy of this incredible journey and how it's reflected in your own ability to move and interact with the world.