Ever owned one of those model-building kits? It’s the kind where you put together little plastic, metal or wooden parts to make a figurine. Characters, military vehicles, gadgets, animals – you name it, they have it. The most basic kits contain just a few parts like the eyes, ears, nose, mouth, arms and legs which you can stick into a ready-made torso. Think Mr Potato Head. At the other end of the spectrum, however, you have mind-bogglingly complex kits with hundreds of parts that can take anywhere from days to weeks to fit together. Model-building is thus a timeless hobby, which over the ages, has entertained a wide demographic from young children to experienced adults.

You may be wondering why I am going into such depth about model-building. Well, I was recently reintroduced to the hobby by YouTube and some colleagues. As a child, I used to collect Bionicle kits from Lego. I would assemble each model and pit them against one another in imaginary battles. Alas, building them became repetitive as I got more familiar with the underlying structure and I quickly lost interest.

Recently though, a video on MythBusters’ Adam Savage building a Gundam model appeared on my YouTube recommendations list. For those of you who aren’t acquainted with Japanese pop culture, a Gundam is a giant humanoid robot controlled by a human pilot in its cockpit. It is one of the many types of pilotable robot that exist in the mechanical-robot genre (or Mecha for short). Since its conception in 1979 by Japanese creator Yoshiyuki Tomino, it has grown a massive fan base and spawned an equally enormous franchise… with TV and comic series, movies, novels, video games and you guessed it, model-building kits!

Going back to the video, I decided to click on it just to see what the hype over Gundam was all about. And, boy was I impressed. The model being featured had multiple layers from an internal skeleton to a supporting frame and even exterior armour. Each of these were in turn made up of an eye-watering number of intricately-moulded plastic parts that snap together – all without glue, tape, nuts or bolts!

Granted, not all Gundam models are as complex (or expensive). Some have fewer layers and/or parts. Yet, their structure reminds me of the human skeletal system, which is the inspiration for this article.

The skeleton of an adult human typically consists of 206 bones. The tiniest bone is the stapes in our middle ear that vibrates with incoming sound waves to help us hear. The longest and largest bone is the femur in our thigh which supports our body weight and helps us to stand. And, if you’ve heard the joke before, our funniest bone is supposedly the humerus in our upper arm. The weird tingling sensation you get when you knock your elbow against a hard surface is actually caused by the humerus momentarily compressing a nerve running just beside it.

I digress. The function of our skeleton is to provide support and protect our internal organs. Without it, we would be a jelly-like mass of organs encased in a bag of skin, which… is at best unappealing and at worst leaves us vulnerable to injury from the barrage of forces we encounter every day. The skull protects our brain. The rib cage protects our heart and lungs. This is just like how the mechanical frame and armour at the Gundam’s torso protect the pilot within its cockpit, arguably the beating heart that keeps it “live” and moving.

Even more amazing is the mobility of Gundam models. Their joints allow them to strike a variety of poses from running to jumping to raising their weapons for battle, and how closely these poses resemble the actual human poise is striking. From my reading, the joint system of Gundam models has undergone a few upgrades over the years and continues to evolve. Hinge joints and ball-and-socket joints feature heavily in the more recent models. These are in fact 2 of the 6 types of movable joints present in humans! The other 4 types are: Sliding joints, pivot joints, saddle joints and condyloid joints. We’ll get to what each of these joints are in a while.

In the context of the human body, a joint is defined as a place where two bones meet. Some joints are immovable, the bones firmly held together by fibrous tissue like in the human skull. Other joints are partially movable, the bones on either side bridged by a layer of cartilage like in the ribs and spine. And, yet other joints are highly mobile, allowing us to perform a wide range of movements from walking to writing (with the help of our muscles of course). At these joints, the ends of both bones are covered by a layer of cartilage for shock absorption and to reduce wear-and-tear. And between them, there is an additional layer of fluid called synovial fluid again for shock absorption, but also for lubrication. These joints are alternately known as synovial joints or movable joints, and are the ones we mentioned earlier. Can you recall the names of the 6 different types?

1. The ball-and-socket joint: As its name suggests, the end of one bone is round like a ball and fits into the cup-shaped end of the other bone (i.e. the socket). A classic example of this is the glenohumeral joint at our shoulder, where the humerus (bone) fits into a socket on the scapula (bone). This type of joint lets us perform rotatory movements – for instance, the popular warm-up exercise of swinging our arms in circles.
2. The hinge joint: If you’ve never given the hinges along door frames a second glance, now’s the time to start. You’ll notice that they only allow the door to swing in one plane of motion – that is, back and forth. Similarly, hinge joints like those at our elbows and knees only allow bending along one plane, widening or narrowing the angle between the bones at either end.
3. The sliding (or gliding) joint: This type of joint can be found where the flat (or slightly curved) surfaces of two bones meet – for example, at the wrist. They allow the two bones to glide over each other freely in any direction along the one plane in which they meet.
4. The pivot joint: At such joints, the end of one bone acts as a shaft around which the other bone can turn. This allows for rotation along one plane, as well as limited back-and-forth and side-to-side movement in the other two planes. An interesting case is the atlantoaxial joint between the first two vertebrae (i.e. spine bones) in the neck. This joint gets its name from the two bones that meet here – the Atlas on top and the Axis below it. The Atlas supports the weight of the skull above it, just like its namesake in Greek mythology who holds up the sky. The Axis, true to its name, has an upward-pointing knob called the Dens around which the Atlas can swivel. This lets us turn our head from side to side.
5. The saddle joint: Never heard of this type of joint before? You’ll be surprised that it can be found in one of the body parts that we rely on heavily every day yet take for granted – the thumb! The saddle joint at the base of our thumb allows us to move it along two planes. We can move our thumb towards and away from our palm. We can also move our thumb back and forth, parallel to the surface of our palm. These movements allow us to hold objects firmly between our thumb and index finger, or grab them with our whole hand. And, given that tool use is one of the features that makes humans so unique as a species, we have our saddle joints to thank.
6. The condyloid joint: Another lesser-known type of joint, the condyloid joint can be found at areas like our jaw and the base of our index finger. At this type of joint, the end of one of the bones is egg-shaped and fits into a similarly-shaped hollow at the end of the other bone. This allows for limited up-and-down and side-to-side movement along two planes. To see this for yourself, try bending your index finger up and down, and wagging it from side to side.

Following this long spiel, let’s get back to our Gundam models. According to lore, they have been and continue to be developed as military weapons. However, the earliest versions of this technology were rather cumbersome and had a limited range of motion. Scientists of the Gundam-verse thus drew inspiration from the human form to improve the mobility and functionality of their designs. It is then no wonder that Gundam models bear so much resemblance to human skeletal and joint structure! There is even a life-sized Gundam at the Yokohama factory that manufactures model-building kits. Standing tall at a whopping 18m, it is able to move, proving that the mechanics of the human skeleton works even at a gargantuan scale!

Having read all the way here, I hope you’ve come to appreciate the intricacies of our skeletal system, as well as the ingenuity of how we humans model our toys (and technology) after what is available in nature. Just to assure you, this article is in no way sponsored by Bandai, the owner of the Gundam franchise. It is simply one science enthusiast turned amateur hobbyist rambling on about the wonders of the human body. Meanwhile, please enjoy this model of the RX-93-ν2 Hi-ν Gundam I have built! 😊

Written by Jacy Mok
Reviewed by Lim Meng Hwee