Ribs are normally seen as 'breath' and 'protection' mechanisms. At school every diagram of how lungs work will have the lungs protecting the heart, and talk about pumping air in and out. I think this completely undersells the importance of ribs and their very central role in a flourishing body.
Fish have ribs. And these ribs are below the 'breathing' apparatus, the gills. So ribs predate air breathing. So their primary role was not breath, but something else.
Ribs do indeed protect essential organs, but then looking at snakes we see that they have ribs all the way along their spine, so they can't be just for protection of those key organs either.
Snakes have huge adaptability and strength and control throughout their body, and can stand 'upright' as well when needed, and strike lightning fast. So ribs must have a strong movement role as well.
So my thought experiment for you is to think about ribs as something very structural, postural and powerful. For a long time I asked clients to turn the word 'rib cage' into 'rib basket' [which is the literal translation of the equivalent term in German] to get them to think of ribs as something which can change shape and adapt. But it is not simply a passive basket - ribs can initiate and support movement, and the 'basket' has power to change shape. So perhaps a better, clumsy term would be the 'rib layer system' which works in partnership with the 'spine layer' to support the spine, to reinforce the spine, lock it down when rigidity is needed, and allow safe movement when you want something more fluid.
You can imagine the spine as something like a tower of cotton reels, with a little, flattened bubble of fluid between each reel and a network of tethers between them, each able to hold the one above in the right position. Then you have a very flexible spine, but it can't have that much strength, and once out of the vertical position it will be quite hard to control and use. But if you surround that jointed, flexible spine with a set of hoops which produce an outer tunnel of fabric which can help the spine stay safe in whatever position or twist it holds, then you have something really special. Think of a traditional tent and how the outer layer of fabric gives 'support' to central tentpole. You can't have one without the other, they are a partnership. The 2 pieces together give you a pretty stable 'space' which can adapt to windy weather if the tensioning system is just right - not too loose or too tight. If one works well, the other can work well. But if one is not working then the other also has to be compromised.
It is true that ribs also provide for protection and breathing; in us, the space between the vertebral system and the outer rib layer system is filled with lungs and heart. The ribs adapted to this additional, key role - providing a system which expands and then shrinks the space, thus enabling us to allow air to rush from one pressure system (outside) into another (inside). We don't 'pump' air into our body, we invite it though differentials in air pressure. It is the ribs which change the size of the space within us and pull the spongy lungs into extension and then fold back to reduce their size.
In modern life, we do few twists and we sit in chairs a lot of the time. We don't continue to use, flex and rotate the rib system. Ribs are very often 'locked' down in some areas. That feeds back into a more rigid and less safe and supported spine. It is the partnership that is important, and one needs the other. That is why yoga and pilates do a lot of mobilisation of the ribs as well as the spine. But if your ribs have stopped moving and got fixed into position, then you can't do the twists. If you try, you can end up putting more, possibly too much, twist into areas which are not fixed down A good twist is spread evenly along the spine, not concentrated in one place rather dangerously.
Some people with ribs locked down feel that they can never get a good 'inhale' and feel short of breath. Others can have a very different experience - their ribs are fixed 'up and out' and they can't ever relax and let their breath out. Both of these limit the capacity of the lungs. Sunken chest and barrel chests are both missing something key. A good breath is one which spreads an expansion of the space within the thorax in an even way, continuously supporting the spine as it does so. In fact, a really good breath lengthens the spine rhythmically throughout the day and night, keeping the spine in good condition. Often people fix their breath every time they move, not being able to do both at the same time.
In your first session with a Rolfer, you will have work on the rib system, work on breathing. We try to find out where your rib system is compromised and uneven, and where it is not showing the flexibility and adaptability that is needed to support and nourish your spine. And we keep working on the ribs and their connections throughout the 10 Series. It is unusual work, but it is profound and always needed. Ribs are quite amazing, but are generally overlooked and under-appreciated. But the secret of a great spine is also great ribs. There is little more satisfying for a Rolfer to feel the ribs waken, and the breath change, and the spine get what it needs.