I don’t know how this learning takes place though as muscle biology isn’t much of an area of interest for me.

Directly attached to the muscles there's tension sensors and a simple feedback controller, in essence you can set a set-point like with a thermostat and the feedback loop will keep the muscle at a certain length. Those are then wired up into groups (not rarely overlapping ones) using further feedback loops, that's roughly speaking the Chinese muscle-tendon lines, turning "lengthen/shorten this muscle" into "open up your hand, the elbow joint, and front of the shoulder", a higher-level movement that's generally speaking bio-mechanically sound (see six harmony movement), using advantageous levers etc. It's all not terribly complicated but is perfectly capable of holding a posture stable against (not too major) interference, it can balance you perfectly on one leg with closed eyes (if you manage to not micro-manage) with an unchanging set of set-points, the actual learning magic happens in the motor cortex (learning how to set the right set-points to achieve a certain posture or succession of postures (ie. complex movement)), which also projects the body's map into the rest of the brain.

Really hard to not think in terms of hierarchy though.

It's what Anarchists call hierarchical realism: We all know the multitude of failure points and issues hierarchical organisations have but often the first reaction people have when being told about any horizontal organisational structure is "that can never work, there needs to be someone in charge" as opposed to "that looks interesting, what are the specific points that we need to be aware of to make this not collapse" -- as if someone was in charge at the grill party last weekend, as if all of the horizontal organisation we're embedded in day to day wasn't actually real, as if order would imply hierarchy.

If you're looking for a systems science textbook there's Mobus and Kalton, "Principles of Systems Science", written for a general audience -- academic, yes, but they're not front-loading it with maths so it's suitable for liberal arts students (SCNR).

But it’s always multiple loops even if the T4 system seems to be separate from our little 60-80 year lives, it’s not.

Back in the days the genome was called "the ancestors" and revered for all the useful information it hands us. It's usually quite abstract, it can after all not anticipate our concrete circumstances. Evolution also isn't random (at least if you ask physiologists): If left to mere chemistry there'd be a disastrously high error rate in DNA transcription, corrective proteins bring that down to practically zero, and then after that is done randomness is re-introduced, apparently in a rather strategic way, to direct adaptiveness: If a bird doesn't get enough nectar it probably doesn't make sense to mess around with mitochondrial DNA, what you want to evolve is the beak shape. Evolution seems to be erm evolved enough to be that strategic, maybe not in all aspects, but in the really important ones (important for fitness, that is).

Sorry that’s more Buddhism than AI or cybernetics.

Hey I'm glad meeting a mind that isn't stuck on either side. Too many esoteric tea-bag swingers on the one side and armchair theorists on the other.