A video showing how human joints contain masterful design is given below. The video contains references to my own research. With thanks to Wayne Begnaud for brilliant work in creating the video.
In September 2024 I published the following review paper in the journal of Biomimetics
How Multifunctioning Joints Produce Highly Agile Limbs in Animals with Lessons for Robotics
A link to the paper is given here:
https://www.mdpi.com/2313-7673/9/9/529
The Abstract is given here:
This paper reviews how multifunctioning joints produce highly agile limbs in animals with lessons for robotics. One of the key reasons why animals are so fast and agile is that they have multifunctioning joints in their limbs. The multifunctioning joints lead to a high degree of compactness which then leads to a host of benefits such as low mass, low moment of inertia and low drag. This paper presents three case studies of multifunctioning joints—the human wrist joint, knee joint and foot joints—in order to identify how multifunctioning is achieved and what lessons can be learned for robotics. It also reviews the multifunctioning nature of muscle which plays an important role in joint actuation. A key finding is that multifunctioning is achieved through various means: multiple degrees of freedom, multifunctioning parts, over-actuation and reconfiguration. In addition, multifunctioning is achieved through highly sophisticated layouts with high levels of integration and fine-tuning. Muscle also makes an important contribution to animal agility by performing multiple functions including providing shape, protection and heat. The paper reviews progress in achieving multifunctioning in robot joints particularly for the wrist, knee and foot. Whilst there has been some progress in creating multifunctioning robotic joints, there is still a large gap between the performance of animal and robotic joints. There is an opportunity to improve the agility of robots by using multifunctioning to reduce the size and mass of robotic joints.
Section 6.7 addresses lessons for the origins debate:
6.7. The Emergence of Multifunctioning in Biology
Complexity in biological systems is sometimes labelled as an emerging property [109]. However, it is very difficult to explain how a multifunctioning system could emerge from an initially single-functioning system because the first single-functioning system would have to be one of the very few solutions that could lead to a later multifunctioning system [106]. When discussing the origin of mechanical linkage mechanisms in animal joints, Muller has stated that it is very difficult to see how complex mechanical linkage systems can be developed in a bottom-up step-by-step process [53]. Therefore, multifunctioning in biological systems such as limb joints presents a major challenge of irreducible complexity for evolutionary biologists [110].
In 2021 I published the following Review paper in the journal of Bio-inspiration and Biomimetics (Institute of Physics)
A review of linkage mechanisms in animal joints and related bioinspired designs
A link to the paper is given here;
https://iopscience.iop.org/article/10.1088/1748-3190/abf744
The paper describes 10 incredible mechanical linkage mechanisms in animal joints. All of them are multifunctioning to some degree. Whilst the paper does not mention irreducible complexity explicitly, it is clear that the mechanical systems are irreducibly complex. As of September 2024 the paper has been downloaded more than 10,000 times and cited over 30 times in other scientific papers. This shows that the paper is seen as important by the scientific community.
Professor Stuart Burgess 