Origins of the Wheel

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It's often lauded as one of those pivotal moments in human history, something that remains fundamental to many of our daily lives down to the present day, the invention of the wheel. When was the wheel first created? By who? And for what purpose? These are questions that have fascinated various scholars for decades, if not centuries.
Opinions remain divided as to where should be labelled the birthplace of the wheel, if there even is one birthplace. Recently, however, a new paper published in the academic journal Royal Society has argued that the wheel was invented in Eastern Europe by prehistoric miners who lived almost 6,000 years ago in the Carpathian Mountains and belonged to an ancient culture known as the Boralas culture.
The argument is that the wheel was invented to help these metal ore miners transport large amounts of copper out of their tunnels. It's a theory that has been around for quite a few years now, pushed in particular by the esteemed archaeologist Dr.
Richard Bullitt, Professor Emeritus at Columbia University. But what makes this latest paper groundbreaking is that the team behind it employed modern science and computing to support the archaeology.
They used powerful computers to create models and simulations to add further evidence as to why this theory that the wheel was invented by copper seeking miners in the Carpathians is likely it's quite scientific but the computer algorithms the team designed appear to reveal just how the wheel might have emerged in that environment and the several innovations it took for them to go from rollers to wheels this is also a a great example of how computer science and archaeology can work hand-in-hand today to allow scholars to make new discoveries about important inventions made thousands of years ago. Now, to unpack this theory and the science behind it, we're going to divide this episode into two parts.
The first part is an interview with Dr. Richard Bullitt to learn more about his work studying the world's first wheels and how he came to the conclusion that the Carpathians were where they were first invented.
Following that, we have an interview with the computational engineer Dr. Kai James, who led this research alongside Richard and Dr.
Lee Alakok. Kai will focus on the science behind this new paper.
He will explain what computational engineering actually is and how he used his skills along with Lee's to create models that support Richard's theory that the wheel originated with prehistoric miners. It's going to be quite the episode.
Richard, it is a pleasure to have you on the podcast today. Tristan, it's very nice to meet you.
Now, I mean, what a topic as well. I mean, the invention of the wheel often hailed as one of those kind of seminal moments in human history.
And yet it feels like it's something that's still quite heavily debated down to today. And even if you can pinpoint it to one place.
Yes. I think that the reason it is debated is because there's no obvious place of origin.
Also, there is the fact that the wheel did not spread very widely in the world. Many societies decided that they did not believe the wheel was worth developing.
You have the Western Hemisphere that had no wheels, but you also have Sub-Saharan Africa

with no wheels.

So while today everyone believes that the wheel is a marvelous invention that can be used for a zillion different purposes, historically, people did not think the wheel was a particularly riveting invention, largely because you cannot separate the wheel from the surface on which the wheel rolls. And if you are talking about simply overland country, you have trees, you have uneven surfaces, it takes a wheel of very large diameter to get over the bumps and cracks and ditches that you find in any landscape.
There are histories of the wheel, but they're not histories of roads. Has there been much debate ranging as to where and how the wheel was first invented? Should we looking at one location or several different locations at the same time, almost spontaneous emergence of the wheel by particular communities? You have essentially three areas that have been put forward as likely starting places.
One of them is Mesopotamia. That's the oldest theory.
So that's Iraq and that area in the Middle East? Well, specifically in Iraq. For example, Egypt did not have wheels, even though it's not that far away from Iraq.
3000 BC is when you have roughly the first evidence of wheels in Mesopotamia, in Iraq. They take the form of pictures of a four-wheeled military vehicle pulled by animals that look roughly like horses, but they're not horses.
And there's sort of a consensus that this animal was a wild ass native to the region. And very recently, it's been established through DNA evidence that the wild asses are actually a hybrid between a domestic donkey and an indigenous wild ass.
So now people are saying that you had a domestic animal called a Kunga, that was in the Middle East, apparently quite some time, but entirely disappeared. In any case, in Mesopotamia, the earliest evidence for wheel is being pulled by a pair of these animals.
So Mesopotamia, that was one theory, wasn't it? But you said there are two others as well. Is Turkey one of those other places? Well, let's say it's the Black Sea, either on the northern edge, which seems more likely because that's a flat plain, whereas the southern is high mountains.
So that the interior of Turkey, and particularly at the eastern end around Armenia, you get the first coming of horses into the Middle East and the connection between domesticating horses and using wheels. Some people have argued that riding horses comes before using horses for pulling a vehicle.
Other people have argued that pulling the vehicle comes before riding horses. But in any case, the connection with horse domestication points to either sort of southern Ukraine or into Kazakhstan or possibly into Turkey, where you have more literary records.
Then there's the third area is basically in Southeast Europe, in the Carpathian Mountain area, where you have no horses back 3,000 to 4,000 BC. So you would divorce the invention of the wheel from the invention of horse harnessing.
And this has not appealed to many people, but I think the evidence is quite strong that this is actually where the wheel first appeared, and then the harnessing of animals to the wheel is a second step. Well, let's explore that now then.
So you mentioned the Carpathian, so Eastern Europe area. And what is this culture that is central to our talk and to your research today, the Borrelas culture? What is this culture? You have a copper age that comes before a bronze age.

And the copper age made artifacts, many of them just decorative, out of copper. And the copper was mined in various places, but particularly the early copper age is in the Balkan mountains and the Carpathian mountains of Southeast Europe.
The bronze age comes a bit later when they start to have tin added to the copper ore, and that produces bronze. But for the Copper Age, it started out with people finding surface deposits with a fairly high copper content, and they could simply roast those and melt out the copper in the stone.
But as the surface deposits became depleted, they started to dig trenches and then tunnels to get at the ore. So the question in my mind, and this is sort of where I started, was what were wheels used for to begin with, rather than how were they built or Where were they found.
Because many people have thought that you would have, say, the big stones or the pyramids or something like that, you'd have to roll them into place. So they thought there'd be rollers.
But the thing is, circa 4000 BC, the loads were either divisible into loads you could handle, just carrying them on your back or even attaching them to a cow or something like that. Most things could be divided into manageable loads or else they were stones that were huge that were too big really to be rolled along.
What you have with mining is that you're moving ore that has very substantial weight, but has very little content of metal. So you have to move tons and tons of ore in order to smelt out a few pounds of copper.
So moving this huge amount of heavy stuff, it's assumed that this was done by people who had baskets or trays, and they would slide the tray or the basket along the floor of the mine. So as you say, it's the copper age and already you've had many years of people extracting copper from the surface.

Those have run out so they're having to mine deeper into the mountains to extract copper. And now it's the technology that they have available to then get those large amounts of mineral, of rock, out of those, should we say mine shafts? Should we be thinking of like narrow? Probably trenches before tunnels.
It depends on how deep you have to go. Because once you start mining, you tend to continue until you've depleted the deposit.
But the Bolarov's culture had copper, but not in huge amounts. Earlier cultures in Southeast Europe had more copper.
But I think as the copper became scarcer because the ores were less rich, you had a stronger and stronger need to move very substantial quantities. And one of the things no one else seems to have paid attention to in the history of all of this is that in Europe, mining continues to use small hand-pushed carts in mines from 3500 BC until 1900.
And the important thing here is that if you have a trench or a mine, you are creating the floor surface that you have to move the ore along as you go. So you're actually building an underground or some surface road to go along with moving the ore.
And I think that that was an important factor because for the first time, you have an actual physical connection that is very logical between the rolling wheel and the surface on which it rolls. You're in a low tunnel or in a trench,

and you've a pathway that you've dug. That is fairly smooth.
If you have a tray or a basket,

pushing it up a slope to get it to the surface, you're basically simply sliding it along.

Now, as soon as you put even one roller underneath it, you're making it easier to move. Dear old work platform, it's not you, it's us.
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Listen to Our Skin on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Do we know what technology preceded it? How these people would have gone from, you know, what they would have been using before and then potentially taking that next step to then create kind of this wheeled transport to transport this copper material out of one of these narrow spaces.
We do have some very early images, but not as early as the Copper Age, of this kind of mining. People, say, carrying things on their shoulder or pushing them a basket.
What happened in the Boleroz culture, this sort of late Copper Age culture in Slovakia, is that they started to drink beverages out of square cups with wheels on the bottom. Hang on, wait.
So this is archaeology discovered from the culture, cups, so ceramics, but they have wheels on them. Yes, or they're built to have wheels on them.
Usually the wheels have not survived, but the holes that the axle goes through have survived at the bottom of the cup. You know, drinking in ancient times in a lot of cultures is an enormously important social activity.
Some cultures will drink out of skulls of their enemies, or they'll drink out of ritons that are sort of long horn-shaped things. But even back to the earliest societies, such as Sumer in southern Iraq, you'll have people drinking out of a common bowl using straws.
So the idea that drinking is a ceremonial activity that is important for the socialization of a culture, but only one place do you drink from cups that have wheels on them. This is not passing the port at Oxford High Table, where you have a trolley that carries the port bottle along.
This is a cup several inches in width and breadth, and you have bosses or protrusions on the bottom with holes in them for an axle to go through. And these cups are not pulled by animals.
They are presumably pushed. You also have a number of the cups that have survived.
We have about maybe 150 examples. 150 examples.
Wow. I'd never heard of them before.
No. Eastern European archaeology, before the fall of the Soviet Union, knowledge of what was being found archaeologically in the Soviet zone and the Western zone was not disseminated very well.
But now these cups have been found fairly recently. And a number of them have lines on the side that make it appear that they are baskets, as if they are just putting wheels on the bottom of baskets.
And again, that sort of points to the mining environment. So I think that you found a mining culture that discovered that they could move ore more efficiently using a wheel.
And then they celebrated their own achievement. And so the primitive mine carts that they developed became a point of cultural pride.
So these extraordinary artifacts, these drinking cups, which represent wheeled transport, these wheeled baskets, the theory is that it's almost the Borrelas people, they are celebrating this invention of theirs to create these wheeled baskets for their mining. And to celebrate this achievement and how important it was to them, you can see them creating miniature versions of these wheels on these very elaborate drinking cups.
Yes. And then once the wheels started to spread, it was no longer that point of extraordinary achievement for other cultures.
They were just having a borrowed technology. But the important thing about these cups that single them out from other early evidence is that they are a type of wheel that becomes obsolete in most environments.

It's not been recognized sufficiently that the earliest wheels come in two different

varieties and substantially different varieties.

The first one, which you have in the Boleroz culture in Slovakia, is the wheels are attached

to the axle in a way that they can't turn.

So it's just straight, kind of going up and down kind of thing, not going around curves

and so on. Yes.
It's very clear that the wheels do not rotate at the ends of the axles. And the way you can tell that, that you have a round wheel, and then you have a hole in the middle of the wheel where the axle goes through.
But in the earliest wheels, that hole is square. So it can't turn.
And we have square holes in the earliest wheels that are found in the Carpathians and also into the adjoining Alps. And these are the earliest full wheels we have.
Whereas in Mesopotamia, we have no example of there ever being a wheel that couldn't turn. So Richard, this is quite interesting.
So it's kind of combining all that information. So you have those ceramics there with the wheels on the bottom, which are celebrating this invention.
And then the discovery of an actual wheel from that area of the world. Is it using evidence like that to kind of create this hypothesis that it was these types of wheels that are invented and the purpose for it is to kind of go up and down these narrow tunnels almost, transporting copper out of the mine, bringing them back down in baskets, getting more out kind of thing.
Is that how it all comes together? Because I mean, I don't know if the Borrelage culture, if a physical wheel is also from that culture, or is that later? The earliest one, I think, is from the Lubyana. The Lubyana Marsh's wheel, yes.
Yeah. And that has a square hole in the center, which means that it could not turn.
I think that the wheels used in the mines were smaller, and they have not survived except in the drinking cups. As you take this new technology out of the mine, and you no longer have a groomed surface for it to roll on, the wheels become larger in diameter because they have to go over a rough surface.
But also, they use them primarily as a pair of wheels in a cart, whereas the cups show two axles, and it's a four-wheeled. What you have in the mine is a small four-wheeled basket.
When it comes out, you have something more like a farmer's cart. So you realize how valuable the proto kind of mine cart that is developed by this Borrelas culture, you realize how important it would be on these baskets for transporting a lot of material out of the mine.
And the mining technology continued to use this kind of wheel down to virtually the present day. When you have an axle and the wheels are attached to the axle, there's a word in English for that.
That's called a wheel set. And that is what railroads run on.
So that the railroad technology comes directly from the mining technology of Bularoz and evolved entirely within the mining community so that the first railroads are simply continuing trackways that are in European mines. And the history of the railroad is very much the modern history of the Bularo's cups.
But in the Middle East, we don't have any examples of wheel sets. In the Middle East, they have wheels that rotate independently.
Now, the exception here is that in Turkey, non-rotating wheel sets were in use up until the present day. Not many of them, but they're a lot easier to build than wheels with spokes or that rotate independently.
So you find a few images in Roman times and then in Turkish history, you find these non-rotating wheels outside the mining context. But otherwise in Europe, it's the mines that preserve the the Bolaraz wheel design.
And once the independently rotating wheels come along, almost everyone switches to that type of wheel, which is easier to turn, but harder to build. This is so, so interesting.
So your theory is that the Borelaz miners of Western Ukraine or of the Carpathian mountains of that region, they invented the wheel 6,000 years ago and it became such an important part of their culture, this kind of basket wheel system. How did you decide you wanted to test this theory with modern technology? What did you decide to do so that you could test this in the modern world? I'm a historian, not a technologist.
I thought that the evidence that I could produce of the continuity of wheel sets from the Boloraz period through European mining up to the history of the railroad made a very strong argument. But there were various technological elements to the argument having to do with when did animals start pulling vehicles, what animals were used for that purpose.
After all, in the Boloraz cultures I mentioned, they had no horses, they had no donkeys. And, you know, to get two oxen side by side in a tunnel, you'd have to build the tunnel much bigger simply to fit the animals in.
So I thought there was a very strong argument based on artifacts. But how the initial breakthrough came, I did not have a clue on that.
I did look at various theories of evolving from rollers, but none of them made much sense to me. And then Kai contacted me and said he had a theory about how rollers could evolve in the direction of wheels.
So this is his contribution. He found the technological key to explaining how this could have occurred.
But there's a lot more to do in this. I think that technological historians have to be aware of how complicated the notion of a wheel is instead of focusing on harnessing the animals, which is very important.
I've written on that subject as well. But it's not just a matter of how do you harness the animals, but it's building the wheel itself and thinking of what's the purpose of the wheel.
After all, humans got along for tens of thousands of years without any wheels. And many cultures, matter of fact, most parts of the world, got along until modern times without wheels.
Okay, then, Richard, you've teed us up nicely to go to the next part of your research, which is then to interviewing your colleague Kai about what he did to kind of move this theory forwards. And Richard, it just goes for me to say thank you so much for taking the time to come on the podcast today.
Tristan, it's been a great pleasure for me to be able to talk about this. Thank you very much for putting me on your show.
So there was Professor Richard Bullitt talking through why he believes the wheel originated with these prehistoric copper miners in the Carpathian Mountains almost 6,000 years ago. How these wheeled baskets made it easier for them to extract large amounts of copper out of their tunnels.
We now move on to the science. Dr Kai James is a computational engineer who worked on this new research alongside Richard and software engineer Dr Lee Alakok.
Kai wanted to see if his high-tech computer models would support Richard's theory

that the wheel originated in the minds of Central and Eastern Europe,

and how, technologically, this early wheel design was invented.

How exactly can computers help with that?

Well, you're about to find out.

Kai, it is a pleasure. It is great to have you on the podcast today.

It's great to be here. Thank you.

Now, we've just heard from Richard about his work and his theory that the wheel originated with these early miners in the Carpathians.

I now want to bring in yourself, Kai, and the science behind this new research.

But first off, I've seen the words computational engineering. Forgive my ignorance, but what is computational engineering? So computational engineering is essentially any form of engineering that uses computers and the power of computers to solve engineering problems.
Often that takes the form of solving mathematical equations. So typically the systems that we engineer are described using physics models.
These models could be from dynamics, solid mechanics, aerodynamics. And so we use computers to solve the very complicated equations that describe the physics of those systems.
And computers do it faster and much more efficiently than if we were to do it by hand. And then we can also involve computers when it comes to things like creating designs or models of engineering systems.
And then more recently, we involve computers in the more creative aspects of engineering. So computers can assist with actual design and helping us make design decisions using tools like artificial intelligence and other related computational methods.
And so what led you to stumble upon Richard's research? And I guess go from looking at maybe modern technology and new ideas and methods and theories and so on, to actually look at engineering from thousands of years ago and the invention of the wheel. What brought you to Richard's research? Yeah, that's a great question.
So it is a bit of a departure from my usual engineering problems that I'm investigating. So my work is in the area of engineering design, using computational methods to design engineering systems.
And typically those are modern engineering systems like airplanes. But I'm also very interested in the underlying theory and philosophy of design.
And so what I wanted to do was see if we could use our computational engineering techniques to perhaps better understand how early engineers, by early in this case, I'm talking about engineers from 6,000 years ago, how they came up with their designs that were revolutionary to them at the time. Also, I wanted to see if we could use computers to kind of mimic that process,

to essentially simulate the way in which early technology evolved.

I started out by attempting to come up with an algorithm that could,

on its own, synthesize a wheel and axle system.

So essentially, the algorithm doesn't have any prior knowledge about what a wheel looks like or how it operates. It only knows that it needs to create some device that assists an operator in transporting some heavy cargo from point A to point B.
That's essentially how it started out. So we created an algorithm that, starting from a black box, could synthesize a system

that ultimately evolved into a wheel and axle. And then from there, it kind of morphed into, well, how much does this computer process resemble the actual process that took place 6,000 years ago when the wheel was invented? and we use this process to gain a deeper understanding

of what that human-based design process, what the human invention of the wheel actually looked like. I guess we sometimes have in our mind, don't we, that one day they have some very obsolete technology almost, or they're doing it all by basket or with a sack carrying the stuff out.
And then the next day they've invented the wheel.

But obviously it's not that straightforward or click of a finger. They've designed this technology.
Is it trying to understand that whole process of human thought as to how they might ultimately reach this end point of this early wheel some 6,000 years ago? Yeah, exactly. We wanted to ask questions like, well, how long did this take? Is this something that likely happened as a kind of abrupt leap in technological advancement? Or is this something that could have occurred through gradual iterations, through a slow evolutionary process, similar to evolutionary biology? Also, we wanted to see if we could learn about the people who were the actual inventors.
And for me, that's been one of the most interesting outcomes of this research, is to gain insights into, you know, why do certain societies arrive at technologies when and how they do, whereas others fail to do so. Absolutely.
So, I mean, that was your objective and seeing, you know, kind of how you could answer those questions. So with your expertise and approaching this topic, I mean, what was almost the start point to create evidence that might support this theory as to how the wheel came to be here? I really just started reading about what do we know so far? What do we know about the origin of the wheel? And so I essentially just looked up various sources, mostly academic journals, so journal articles, but also read a few books from various scholars of the origins of the wheel.
And one of the books that I looked up and that I ended up reading was the book written by the man who became my co-author, Dick Bullitt, who's a historian of technology. And I knew that working with him would greatly enhance the project.
Well, for one, the credibility that I would receive as sort of an engineer entering this realm that is not really my own. But also having his insight as a historian, I thought that it would make for a really powerful collaboration.
And so that's how the collaboration came about. I found his book, read it, found it really interesting, reached out to him, he responded.
And so we had a Zoom call where I pitched my vision, my ideas, my hypothesis, and he was on board. And a lot of our thinking about the origin of the real really lined up with one another.
And so that's how the collaboration was born. And if you don't mind, and I've read your paper alongside, you know, Dick and Lee as well, Lee's the third author in that paper.
Yeah, he's the first author. He's my former PhD student.
So he did basically all of the computer programming and mathematical derivations under my guidance. So yeah, he was a huge driving force in the project as well.
And I've read through it and I noticed when you get to the methodology and what you guys did, there are lots of big, and I must say, complicated equations for me as a Joe Bloggs, looking at this from the outside. What were some of the main algorithms that you created that helped you advance this research and ultimately come to your conclusions, which we'll get to in a bit? Good question.
So I would say there are three major components. One component was a modeling or simulation tool that we used in order to predict how the structure that comprises the wheel and axle, how it would respond to loading.
So the wheel, we think of it as a mechanism, but it's also a structure. It's a rigid structure and it has to be designed to withstand significant loading.
This is key, right? I mean, so the wheel in essence is a, or at least at the time was a cargo carrying device. It was used to carry heavy loads that would have been very difficult to drag or to haul.
So it had to be very structurally rigid. And so we created an algorithm that would simulate under these loads, how would the wheel and axle respond? How would it bend? How and when would it break in response to that loading? That was component one.
And then additionally, we had another module of this broader algorithm that was designed to calculate how much effort would be required to push a cargo of a certain weight given the wheel's design, right? So if your wheel looks like this, if your axle looks like this, and if the amount of mass you need to a cherry is 100 kilograms, how much effort or how much force would be required to push that weight along the ground? And so that was another calculation that the algorithm performed for us. And then the third component was what we call an optimizer.
So this is a third software tool that communicates with those first two modules and says, okay, this is our current candidate design. Tell me how does it perform in terms of efficiency, right? How much effort is required to push our mass given this design? And how does it perform in terms of structural integrity? How stiff is it? How likely is it to break under this load? And so the optimizer, this third component, takes that information and modifies the design ever so slightly in a way that improves it incrementally.
And so that process takes place in an iterative fashion. It goes through repeated loops of this cycle until eventually it converges on a design, a shape of this system that is optimal.
And what that process ended up revealing is that the optimal design given the particular objectives of the users of the wheel was essentially you know a slender axle capped on either end by two round discs which we now refer to as wheels and that optimal design just to give us a refresher what richard said earlier it's not kind of deep tunnels with big corners that you think of maybe from the wild west or much later these are small tunnels but straight tunnels as well this is to wheel stuff out in a straight line so those are the conditions that you're thinking of from 6 000 years ago exactly the nature of this design really fits well with the idea of the mine environment because it was likely straight, we know that early wheel and axle systems, because they were what we call monolithic structures, they're a single part, right? And if you rotate it, everything rotates in unison, as opposed to a multi-body system, where you have a separate axle and two wheels attached to it, but they can rotate independently. And a monolithic wheel and axle system can't navigate turns.
So the mine environment is one that would have been conducive to this particular very primitive version of the wheel technology. The other thing about that type of wheel is that it also required very flat terrain,

level terrain, and firm terrain. And that also is where the mine environment, we believe,

played a key role in allowing this technology to involve. Because if it had been used for farming

and it was used to carry harvest through a field, that terrain wouldn't have been covered. It would

have been less processed, so it would have likely been less flat, less firm, probably not level. The mine environment is very different.
And so that's why we think that this society, which as far as we know, had no written language, very little mathematical or scientific sophistication, their particular circumstances were such that they were in the right place at the right time. Whereas, by contrast, a civilization like the Egyptians, who were highly mathematically advanced, highly scientifically advanced, and had obviously every opportunity and every need, had a dire necessity for the wheel, you know, during the building of the pyramids, they apparently did not know about the wheel at the time that they built the pyramid.
So it goes to show the importance of environment in this technological development process. I mean, it really does.
And it's such an interesting piece of research to do because remember Richard saying how you have those clay figurines, which shows kind of that design, almost the end product from that environment and maybe how they were celebrating that technological invention. So you almost say you have an end point to know, okay, that's what they reached.
My other question then is, do we know the key steps of innovation or did your research reveal more about what we think the key steps of innovation were for these people to ultimately reach the wheel? Because you mentioned ancient Egypt there, and sometimes you see pictures of them bringing up large blocks of stone or whatever, but with rollers. I mean, and that's a word that I do want to ask, because do we think it goes rollers to wheel? Or what else did your research suggest about that whole innovation, the steps of innovation to finally reach the wheel? Yeah.
So our theory is that it started with rollers. Historically, this has been the subject of controversy.
I would say up until about 60 years ago, it was relatively uncontroversial that wheels evolved from rollers. And you can kind of see why it's very intuitive.
A roller is very similar to a wheel in its geometry and the way in which it operates. And so the theory was that they started out using rollers and then over time, the center region of rollers kind of hollowed out, revealing a slender axle.
This actually began to be called into question on the grounds that rollers do not perform well in most environments. Because they require firm terrain, they require flat and level terrain.
Rollers have not been used very widely throughout history. And so the argument was sledges or skids essentially sliding your cargo along the ground on some type of sled.
People believe that was the more likely precursor because they were much more widely used. Our theory is that yes, rollers were very rare, but so is the invention of the wheel itself.
If you look back through history, independent discovery of the wheel is something that may have occurred as little as twice throughout the entire history of humanity, which suggests that the inventors were doing something that was unusual, that wasn't very common. And the theory that they were invented in mine, or invented by people who wanted to use them in a mine, fits this puzzle, right? It kind of explains why it's so rare and why this very niche technology, which is rollers, would have been the likely precursor.

In a sense, we kind of resurrected the roller theory, which was the prevalent one until pretty recently, but we made some modifications.

Earlier theories about how that sort of shape change took place left out a few steps that we included and we were able to show that these steps were necessary using our mathematical models. Work management platforms.
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Visit Raisin.com and start saving smarter today. Let's explore these various steps, Kai, because i do see in your in your paper that you have a few visual images of almost the stages to creating you know this early wheel type so let's explore this so step one is you start with rollers so these are cylinders that you know are placed on the ground in an array, you know, side by side.
Made out of wood. Yeah, they could be made out of wood.
They could be made out of logs. And so you place your cargo likely in a cart, some kind of container, and you just push it along.
And the rollers are rolling along the ground. But the rollers are also rolling with respect to the bottom of the cart that's resting on them.
And so we refer to that as bilateral rolling because it's rolling that takes place on two different sides of the roller. There's the roller ground interface and then the roller cart interface.
Both of those are roller surfaces. And under ideal conditions, there's no friction involved in that process.
So it should be fairly easy if you have the right conditions, if your ground is flat, firm, and level. The problem with rollers, however, is that once your cargo passes a roller, it becomes useless.
So those rollers that we call them spent rollers, right? So they're rollers sort of that you've already passed. They're at the back end of your path.
Those rollers need to be replenished. So you typically would take those rollers and bring them around to the front of your cart.
And so in a mine or in a tunnel, this process becomes very onerous. Even though the ground, the terrain in a tunnel was conducive to rollers, the fact that it's an enclosure also means that rollers have this additional requirement that is very costly.
And so we believe what happened was the first innovation was to create a socket in the bottom of your cart or your container that the rollers would rest in. And so as you pulled your cargo, the rollers would be pulled along with it because the rollers are sitting inside the socket.
So you no longer have to bring those spent rollers around to the front. It's almost kind of like a sledge, but a sledge that is rotating there, isn't it? Exactly.
So that's step one. Now, the problem with this step is that it reintroduces friction.
So rather than a bilateral rolling scenario, now you've got rolling on one surface, that's the roller ground interface. But where the roller meets the socket at the bottom of the cart, that's a sliding surface now.
And so you're going to get significant friction there. And in fact, this is mechanically equivalent to just dragging your cargo on the floor.
So we believe that this was overcome by placing grooves in the rollers so that you could apply lubricant. And with the right lubricant, the right surfaces, you can reduce the pushing force required by a factor of three or more.
That step is something that wasn't addressed in previous

theories about evolution from roller to wheel. And then the key step, once you arrive at unilateral rolling with lubricant, the next step is the shape change.
We argue over time, the region in the center of the roller started to become more and more narrow. Now, initially, this could have been so that the operators of these carts, the miners, could achieve clearance.
So if you had small objects on the ground that may obstruct your pack, if you hollow out the roller in the center, you can just roll right away. It gives you that space from the bottom, yeah.
Exactly. But what they would have found is that as a result of that hollowing out, the pushing force actually went down.
And so this is one of the key contributions of our paper. So we derived an equation that shows that as the axle gets more and more slender, the amount of pushing force decreases proportionally.
So if you can reduce your axle so that its radius is one-tenth the radius of the wheel itself, right? So the outer portions, the wheels, those are still in contact with the ground. If the axle radius or the axle diameter is one-tenth the diameter of the wheels, then you only require roughly one-tenth the force to push, right? So we derived an equation that showed that relationship.
And so they didn't necessarily need to know that equation. I'm sure they didn't.
But what they would have noticed is that those rollers that had very slender central regions would have been a lot easier to push. And so this is the third innovation.
And so that is essentially a wheel. And in the paper, we call this a wheel set because it's a monolithic structure.
It starts out as a roller and essentially you carve the axle out of that log, that cylinder. And so the axle and the wheels rotate in unison.
At that point, you're pretty much done. You have a wheel and that type of wheel still exists today in certain contexts.
the wheel like all technologies is a dynamic and evolving thing i think you're right we could talk a whole hour about you know all of these wheel innovations but it's been fascinating one of the main things i've taken away first of all just thinking of how the design changes for it to ultimately i guess yeah just smallen the roller into an axle and then you have the rest of it there. And it was difficult for me to get my head around before talking to you, Kai, about that whole process of going from roller to wheels.
But I mean, you've made it sound so much clearer now and it's so interesting to see how that thought process may well have gone. And also your work around this and Lee and Richard about this kind of evolution of the world in that particular environment in the mines from 6 000 years ago i guess it begs that last question doesn't it i guess this is a question that maybe you're not designed to answer with your research but to think you know potentially just how long it took for these people to go from one step to the next it's really hard hard to know.
And this is one of the challenges with trying to understand deep history from times and places where the way things played out wasn't documented right there. So it's really hard to say.
And the other thing is, we believe that those less efficient versions of the wheel, for example, the grooved roller, which was kind of the first innovation, those things wouldn't have lasted very long because they were solid efficient. And as a result, these intermediate technological steps often don't make it into the archaeological record.
Because in order for things to last thousands of years,

I mean, statistically speaking, there needs to be many of them. And so because we don't have artifacts of those intermediate technologies, it's very hard to say.
I suspect though that those intermediate technologies wouldn't have lasted very long. I would place it on the order of maybe a few decades just because they were so inefficient.
And in fact, biology, right, and biology of living things evolves often in a similar way. So it's referred to as punctuated evolution.
Species will undergo rapid transformations over a small number of generations until they reach some optimal or stable design. And then that design perseveres for many centuries, millennia, or maybe even millions of years in the case of some species.
And so we believe that the wheel set is one of those locally optimal designs that persevered. And we still have it today for that reason.
The intermediate steps, because they were suboptimal, didn't last very long. And so it's very hard to get an accurate picture of how long they would have been in place.
One other thing that you mentioned there, which I found so interesting, was how you mentioned you need to have those optimal conditions for the creation of the wheel and then I guess you can understand why certain parts of the world you know the wheel doesn't evolve until much later be brought in much later because you mentioned Egypt and so on Kai I must ask to finish you have just done this research alongside Lee and alongside Richard this is you delving into archaeology and ancient history and you now you can how amazing it is. But what's your plan next? Do you plan to do more research around early wheels or another part of ancient engineering or technological discoveries? What's next for you and your research? So I have a couple ideas in mind.
This type of work is really just one part of my portfolio. So I still work on more conventional aerospace engineering problems like optimal design of electric aircraft and that type of thing.
But as far as my forays into ancient history, I would like to see if we can use these tools to understand other seminal technologies, like, for example, the bow and arrow, which is another really fundamental mechanical invention that, somewhat unlike the wheel, pops up in many different places and is discovered by many disparate civilizations that had no contact with each other. In that sense, to me, the bow and arrow kind of represents, like the wheel, an underlying

fundamental truth about our physical environment.

So I think it's just really cool that these different civilizations all kind of came up

with the same idea.

And so it'd be interesting to use physics and computational engineering to get a sense

of why.

And then also, I think my next project will be a little bit closer to home. I want to look at the invention of the airplane.
And so that one's different because this is, we're talking about 120 years ago. So its evolution is somewhat well-documented, but I have a theory that the true invention of the airplane and the innovations that led humans to achieve flight actually took place much earlier than the Wright brothers.
And so I think that the evolution is more complicated and more nuanced than even aerospace engineers truly understand. So look out for that.
It might be a bit too modern for us, I admit kai however there are other podcast history of podcasts that would be fascinated by that and that bow and arrow stuff is certainly in the ancients wheelhouse so i will keep an eye out for that research when it comes around and we'll have to get you back on then but it just goes to me to say kai this has been fascinating to interview you and richard before you about this extraordinary new paper that has been published around the origins of the wheel some 6 000 years ago and it just goes for me to say thank you so much for taking the time to come the podcast today nice lot first and i really enjoyed it well there you go there was dr kai james and before him dr richard bullet talking you through this exciting new research into the origins of the wheel, looking at the archaeology, the theory of it emerging with these Carpathian miners some 6,000 years ago seeking copper, and also this new science, the use of computational engineering to try and understand the evolution process of the wheel in those minds and how the environment was right for those innovations to happen step by step. Thank you for listening to this episode of The Ancients.
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