[00:00:04] Speaker A: Id the Future, a podcast about evolution and intelligent design.
[00:00:12] Speaker B: Welcome to id the future. I'm your host, Brian Miller. Today, my guest is Stuart Burgess. Doctor Burgess is emeritus professor of engineering design at Bristol University and an adjunct professor at Liberty University. He has published over 200 scientific papers on engineering design and biomechanics. He has led the design of the chain drive for the British Olympic cycling team for the last three Olympics, and exhibited his work at the Royal Society in London. He has received many academic awards, including the Imech e Claydon Prize in 2019, a top mechanical engineering prize in the UK, the Turner's gold medal for spacecraft design, a design council prize presented at the UK Minister of State for Trade and Industry, and the Wessex Scientific Medal for work in biomimetics. Today, we will be discussing his recently published paper in the journal Biomimetics, which is titled how multifunctioning joints produce highly agile limbs in animals, with lessons for robotics. In this article, he further demonstrates the genius of the design behind animal limbs. So, doctor Burgess, thank you for joining us.
[00:01:22] Speaker A: Yeah, it's very good to be here. Thank you.
[00:01:25] Speaker B: Well, I'm going to. We'll just have a nice discussion about your paper. And I want to begin by asking you, what do you mean by multifunctioning? Because the point of your paper is that the multifunctioning capacities of limbs give it enormous advantages. So could you please define that term?
[00:01:44] Speaker A: Yes. So, for an animal joint, it generally means using the same set of bones to perform different functions. So, just to give you an example, in the case of the wrist joint, there are eight small bones called carpal bones in the wrist joint. And those same eight bones can perform four different functions which affect, firstly, flexion extension, secondly, abduction adduction, thirdly forming a carpal tunnel, and fourthly, transferring loads of. Now, just to clarify, not all eight bones are involved in all four functions, but most of them are, there are between six and seven bones involved in each individual function, as I explain in my paper. So this multifunctioning ability is why engineers call the wrist joint a masterpiece of engineering.
[00:02:40] Speaker B: Oh, and in your paper, what I particularly appreciated is how you describe the advantages of how joints can be multifunctioning. So, for instance, you mentioned such advantages as compactness and energy efficiency. Could you provide some examples of these advantages?
[00:02:58] Speaker A: Okay, well, first of all, compactness is really crucial in engineering, and I think this particular performance aspect is often underappreciated. For example, a space graph needs to be compact to fit inside a rocket car. Systems need to be very compact, fit in the envelope of a car. And it's the same for animals. Compactness is crucial to their performance. So just to give you an example, in the case of the wrist joint, there is really remarkable compactness. The wrist joint has a volume not much bigger than a golf ball, which is really quite incredible. But by being compact, this enables the hand to fit into tight spaces, which is very important for skillful tasks.
But that compactness also means that the wrist is extremely lightweight. If the wrist, for example, had four different mechanisms for the four different functions, it would be so much heavier than it is at the moment. And because the wrist is at the end of the arm, at the end of the limb, that weight would really hinder movement. Compactness has a whole host of benefits of being smaller, slender, and not just having a smaller weight, but a smaller moment of inertia for a moving limb.
[00:04:26] Speaker B: Now, you described in beautiful detail some of the strategies that are used to achieve the multifunctioning capacity. Could you describe some of the strategies that you detailed?
[00:04:38] Speaker A: Yeah, this was one of the really interesting things that came out of my research, because some of these things are not always obvious. But having spent years looking at wrist joints, knee joints, ankle joints, I could see these common strategies. I mean, the first one really is through very clever design solutions. So, for example, I mentioned the wrist joint. Already. The eight bones of the wrist joint have an ingenious arrangement, like a jigsaw, where they form arches in different planes and they have a very particular shape that enables this to happen. I mean, that is just really clever design. In fact, both the wrist knee and ankle have very, very clever designs. And one of my recommendations for robotics engineers is to try to be very creative with the design and geometry of the joint.
But the second strategy you see in joints is to have segmented bones.
For example, in the case of the wrist, the eight bones form a kind of rectangular network of bones. In the case of the fingers, there's a series of small bones. Of course, in the case of humans, there are three bones in each of our fingers. But in the case of some whales, there are up to 14 bones. For example, in the pilot, well, up to 14 bones in their fingers. So you have these networks of small bones now. So why is this important? Well, it's really important in that it gives a smooth curvature and this is often important for performance. For example, in the case a whale flipper or a bird wing, when those limbs deform, a smooth curvature is maintained, and that enables, for example, the whale flipper to maintain a low drag coefficient. And also for the bird to maintain a low drag coefficient by having this smooth curvature. So these networks of very small bones in the wrist and also the ankle of the different limbs is a really key design feature that helps keep a smooth curvature. And that really hadn't been highlighted before. So that was one of the highlights of my paper drawing attention to this particular design feature, which I then recommend robotics engineers to use in their designs, because that has not been picked up by engineers designing robots before.
[00:07:23] Speaker B: Now, in your paper, you also describe how it's not just the bones, but many other features, like tendons and muscles, have to also be very carefully engineered to support the bones. And one of the most interesting example is you mentioned the need for sensors. Would you please explain why they are needed?
[00:07:42] Speaker A: Yes. Yeah, that's right.
I mean, one reason is that multifunctioning joints are often what engineers sometimes call under constrained. For example, in the case of the knee joint, without muscle control, the knee joint can move in all kinds of directions, because the knee joint can both flex and rotate at the same time.
And so it takes fine control with the muscles to keep it stable, to give stable, predictable motion.
And in order to have fine control, you need a lot of sensing to know where the knee is. A remarkable feature of animal joints is that they have many, what's called proprioceptors. These are sensors within muscles and other parts of the joint so right inside the body that monitor the position and velocity of joints. This is something engineers do, although in the case of the body, there are many more of these sensors than an engineer would put into a robot. We have thousands of these position and velocity sensors in our joints. The brain needs all this information because it needs to know the position of the joints in order to instruct the muscles to produce the forces that will produce the required stable motion.
But I should just add one other thing. An additional reason for the sensors is that it enables controlled movement in unpredictable terrains.
The main example of this would be if you're running on uneven ground, your ankles and feet are going to be twisting and turning and potentially throwing the body right off of a stable path. But the brain is able to rapidly make corrective adjustments to the joints, all of the joints, hips, knees, ankles. And the reason it can make those rapid adjustments is because of all those thousands position and velocity sensors in all the joints. So sensing is really, really important. And this is something that robot engineers are appreciating because they're trying to produce robots that can walk and run, although that's a really hard task.
[00:10:03] Speaker B: Well, that's amazing. I had never even thought about what you just described. Now, from your experience, how difficult is it to design something like a robot limb or a structure that's similar to life? Is it something that can be done pretty easily by a novice, or does it require a high level of skill to make this work?
[00:10:23] Speaker A: Basically, the answer is, it is very difficult. And you can actually prove this by looking at either prosthetics, human prosthetics, wrists, arms, hands, or looking at robots. You will always notice that robots are bulky, clumsy compared to human limbs, and the same with prosthetics. They're always bulky.
There are thousands of engineers working really hard and making quite good progress, but limited progress because of the difficulty in doing this.
And there's a host of reasons.
One of them, a key reason, is it is very difficult to produce an artificial muscle that matches human muscle. I've actually published research myself on dielectric elastomers trying to produce an artificial muscle. I know from first hand experience that engineers cannot match the power density of muscles, the compactness of muscles, the response of muscles. So that's one key reason producing an actuator is good as muscle. But it's not just that engineers cannot produce the lubrication that the human body has, the synovial lubrication. It has a. A special lubrication regime. Regime elastrohydro. Dynamic lubrication that engineers cannot replicate.
Engineers cannot replicate human ligaments, especially their strong joints, with the bones.
And engineers find it hard to replicate the sheer precision that we find in joints. There's a whole host of reasons, and, I mean, a good example, if you wanted to look into this, is to look at engineered prosthetic wrist joints. And you will see very clearly that no engineered prosthetic wrist joint comes close to the compactness of the human wrist joints. The prosthetic joints are always very, very bulky and relatively clumsy. So it's a great challenge, but it is employing a lot of engineers to address that challenge.
[00:12:34] Speaker B: Wow. So you've made just a really strong case that life is both demonstrating truly genius design that's far superior to human engineering in many ways. But an evolutionist might argue that there could be evolutionary routes for this perfection of design to come about. So, for instance, they might argue that a series of mutations manufactured a limb like a hand, to perform some function. And then perhaps another set of mutations enabled the limb to perform other functions in a gradual way. And then maybe more mutations modified the limbs with the help of natural selection and crafted sensors to optimize all the functions. Is that scenario realistic? Is that something that human engineers could do? Like, what's your view on that claim?
[00:13:24] Speaker A: Yeah, I think that's not possible, particularly because of irreducible complexity, and I'll give a couple of examples of that. Actually, before I do that, I will kind of mention a general point that if it was possible to step by step, produce the designs of human joints, then engineers would have done it a long time ago, because then it wouldn't have been that difficult. But I will come back to irreducible complexity. Some single functions in human joints are irreducibly complex. For example, the knee joint has a wonderful four bar linkage system through the two cruciate ligaments that only work when all of the linkages are present and assembled. Engineers know that you cannot evolve a four bar linkage step by step. The whole thing has to be there. Another example would be in the foot. The foot has an arched structure that only functions when all the parts are present. It's well known in engineering that you have to have a whole arch present all at once. You can't evolve it step by step. So, joints have good examples of irreducible complexity, but multifunctioning presents an additional layer of irreducible complexity, because the first solution for the first function would have to be one of the very few, if not unique, solutions that also has the potential for producing the later functions that would later be added and that would normally need, or, you know, virtually always needs, forward planning by an engineer. So, in other words, multifunctioning greatly narrows the solution space. And so if life has evolved by chance, you would not expect animals to have so much multifunctioning. And yet animals are full of these multifunctioning joints. And just to add, in my paper, at the very end of the discussion, I do mention this point that multifunctioning presents a very serious challenge of irreducible complexity to evolutionary biologists. And the reviewers thought that was fine to have that in the paper. So the reviewers agreed with me.
[00:15:48] Speaker B: That's amazing. I mean, this is. I love how your research is just overturning so many myths about poor design and just showing how only an engineering framework helps you to understand this genius of design. But there is one other criticism I want to address, because many biologists have argued that many features in the human body appear poorly designed. For instance, and you've spoken about this biologist before. Nathan Lentz wrote the book human error is a panorama of our glitches, from pointless bones to broken genes. And as but one example, he argues that the interior cruciate ligament, or ACL, is poorly designed since it tears so often. And I just had two questions. One is, how did he come to this conclusion? I mean, did he interview engineers that helped him to do detailed analyses? And secondly, does your research challenge this claim?
[00:16:43] Speaker A: I'm pretty certain he has not spoken to engineers or sports scientists, because if he had a, they would have told him he's wrong. I've published quite a number of papers on the human knee joint, including its optimality, for example, in journals like the American Society of Mechanical Engineers, the Journal of Mechanical Design, and Journal of robotics. In those papers, I've said the knee joint is an optimal design, which is also what you would find if you read journal papers by sports scientists. And what they say is that when there are problems with the knee joints, it is to do with misuse, not to do with the design of the joint.
I can.
I mean, just to. Just to back that up. If you go back a hundred years, you find that snapping of the anterior cruciate ligament is not a common injury. Today, it is much more common. But it wasn't common 100 years ago. So 100 years ago, it's clear that it's not a bad design. There are particular reasons why we are seeing more problems with the anterior cruciate ligament, just to give you three examples. Number one, many children in western society, particularly in the United States, are not very active. And it's been proven that when children are not active in terms of climbing trees, running around gardens, later in life, they have weaker joints, more chance of arthritis, and more chance of problems with ligaments.
Secondly, in modern society, many adults are overweight, particularly true in the United States. And if you are overweight just by, you know, half a dozen pounds, a dozen pounds, this has a huge effect on your joints, you know, a negative effect on your joints. Thirdly, more adults today do dangerous sports, or kind of dangerous sports like skiing, skateboarding, bmxing, and those can put really unnatural high loads on your joints. Now, if you add those three things together, and there are even other things, but if you add those three things together about modern society, that begins to explain why you have a higher prevalence of such injuries today. I could mention other things like people think, oh, I can do something risky because there are hospitals today. That's not something people said 100 years ago, but people take more risks today. So I think the reason people have these problems is to do with misuse, not to do with the design of the joint itself.
[00:19:35] Speaker B: Now, one of the points you've made previously is that often, biologists like Nathan Lentz, they only look at one variable and they think, well, if the ligament was thicker, that would be better because it wouldn't tear as often. But as an engineer, what you do is you look at all the different variables that are relevant to this structure. So, for instance, let's say Nathan Lentz got his way and people doubled the thickness of a ligament. Would that cause problems to the design?
[00:20:06] Speaker A: Yeah, I can see. Some people would say, well, wouldn't it be a good idea to have a big design margin and double the size of that anterior cruciate ligament? And then I could do these dangerous sports. But then you would start to lose the compactness of the knee joint, because not only would you have to double the size of that ligament, you'd also be having a bigger connection. You're starting to lose compactness and lose performance. So you don't put an extra margin in just for the sake of it in order to do some dangerous sports. A good engineer will never put in an extra margin just for the sake of it. But I just want to make one more point about the size of the cruciate ligament, because the anterior cruciate ligament does actually naturally increase if you gradually build up your exercise. So if, if you do weight training and say you're a footballer and you gradually increase your training regime, your anterior crucial ligament does increase in size. That's been demonstrated. And in fact, by definition, the whole body adapts every single ligament and tendon and muscle to what is required. So if you train properly and build up your training gradually, you will actually have the optimal size of ACL, by definition, for your sport. So yet another reason why some people have problems is they do not build up their training gradually. They suddenly start skiing without lots of gradual practice. And yes, their knee cannot cope with the skiing manoeuvre they do, but it's because they didn't build it up. They just thought they could suddenly rush into this sport. So it's quite a complex picture.
[00:21:54] Speaker B: That's extremely insightful. Now, is Nathan Lentz an anomaly, or do other biologists without engineering training identify biological features as poorly designed? Are there other examples of this?
[00:22:07] Speaker A: Well, I've had the pleasure, privilege, of working with many biologists. When I worked in the states. At Liberty University, for four months, I was embedded into a biology department, really enjoyed working with biologists. And one thing that really struck me, if you work with biomechanics engineers and biologists, I was really struck by how many completely agreed with me that the human body is incredibly well designed.
I met very few atheist skeptics in that community. So yes, Nathan Lentz is very unusual. He's absolutely not typical at all.
I think people like him very clearly have their own agenda. And his agenda is he's anti intelligent design. That's what drives him. He's not driven by particular evidence. In fact, he seems to not understand what the evidence is in terms of biomechanics.
So yes, he is not a typical academic.
[00:23:17] Speaker B: That's right. I'm really glad you said that because I realized when I heard people say that so many features of the human body or other animals are poorly designed. These lists often appear on atheist blogs. So that's actually really helpful for you to mention that the biologists who are most knowledgeable of the field recognize that genius and optimality design is common.
Thank you.
[00:23:42] Speaker A: Yeah. Just to add one point, I'm heavily involved with biomechanics journals. I've been editor of the Journal of Design and Nature.
I've been a guest editor of the Journal of Biomimetics. These journals have an assumption that nature has the gold standard of design. And if you read through these journals, thousands of papers will, will always give the message, nature is the gold standard of design. We should copy it. And it is the complete opposite of reading a book by Nathan Lentz or Jerry Coyne or Richard Dawkins. It's like chalk and cheese that they're speaking a completely different language. So the engineering community, the biomechanics community, sees nature, not just the human body, but the whole of nature, as the gold standard of design. And as a default, you should always copy it.
[00:24:39] Speaker B: Well, thank you for joining us. That was amazing. Now for our listeners, if you would like to learn more about Stuart Burgess's work, you can go to his website, which is professor, that's P r O f, Stewart burgess.com, that's HTTPs.
And if you want to learn more about his research, I have an articles that have come out on his previous paper on evolution news, and I'll have an article about this paper that'll come out shortly. So thank you for joining us for id the future. I'm Brian Miller, and we hope to see you soon. Have a good day.
Visit
[email protected] and intelligent design.org dot this.
[00:25:22] Speaker A: Program is copyright Discovery Institute and recorded by its center for Science and culture.
