What a genotype is, and is not

Open a whole-genome file and tens of thousands of variants line up in front of you. Try to find a meaning for each one and you stall almost immediately.

Most of the time, what a variant sets is not a conclusion. How fast a given enzyme works. How readily a given receptor responds. These are small adjustments to individual functions, particular to you.

I think of the work as reading the manual for one specific physical system. The manual says what this machine tends to do well and where load tends to accumulate. The strength or weakness of any single function does not map directly onto who a person is.

Reading a fixed blueprint and reading a daily record are also two different things. Separating those two is where I start.

Staring at a list of variants does not make meaning appear.

Metabolism runs as a pathway. A slow reaction causes no backup if there is enough slack upstream of it. Conversely, a reduction small enough to look negligible on its own will hold up everything downstream if it happens to sit at the rate-limiting step. Where the bottleneck is can only be seen from inside the pathway.

So what the work produces is not a list of variants. It is a diagram of pathway structure.

The pathways covered here form a hierarchy. Lower layers hold up the ones above them.

This is the part that looking only at genotypes will not reach.

Sound, light, electromagnetic fields, information. Each of the four enters by a different door. Light reaches the body clock from specific cells in the retina. Sound travels the auditory route, and part of it arrives at the emotional centres before any thinking happens. Information, once taken as meaning, rewrites how the body feels to itself.

Different doors, different speeds. And yet in the nervous system they converge on a single point — the balance between excitation and inhibition.

The genotype sets the substrate of this pathway; the environment becomes the input to it. Neither one alone accounts for what is happening in a particular person.

So the reading does not end with the genotype. Which inputs is this substrate sensitive to? Seeing that as a structure is part of the same continuous piece of work.

One more step outward on the question of inputs.

Cognition comes in roughly two modes: one that runs fast and automatically, and one that lines up symbols and thinks slowly. I will call them S1 and S2. S1 is carried by the monoamines and their receptors; S2 by glutamate and the prefrontal circuits. In terms of the hierarchy above, they correspond loosely to the modifier layer and the base layer.

What is easy to miss is that neither of the two is contained inside the body. Both have parts implemented outside it.

The outside machinery acts on the inside. Ritual and embodied practice set the baseline of the autonomic system and the monoamines through repetition. Habituated norms, religious taboo, morality and law hold impulses down from outside. Recommender algorithms and affect-driven media strike the same reward circuitry from the opposite direction. The machinery that restrains and the machinery that provokes are aimed at the same internal implementation.

On the S2 side, writing and records, the formal systems of mathematics and logic, education and knowledge bases have all worked as external memory, extending what the inside can hold. Generative AI joins that line. It can serve as scaffolding or as a substitute, and if you hand everything over, the inside simply goes unused.

Which brings me to the point of this section. Much of what we call individuality is not settled by the genotype alone. Two people with the same substrate — one living where formal practice is built into the day, the other where a recommender algorithm runs continuously — will not present the same way. Social infrastructure is not a metaphor here. It operates as part of the person's cognition.

So the reading looks at both: the substrate, and the scaffolding it stands in. The reason it does not end with the genotype is not only the physical inputs described above. There are these inputs as well.

There is a view I hold as a working criterion while doing this reading.

Health is not which state you are in. It is whether you can move to the appropriate state at the appropriate time.

Concentrating. Unwinding. Letting thoughts reorganise. A living system moves between these three. Trouble usually appears when it becomes stuck in one of them.

High arousal is not itself a problem. Arousal that will not release is. The same holds for sedation. Not which state is better, but whether the move is available. The body solves this by how it apportions the substances that modulate the nervous system.

I read metabolic pathways with the same question in mind. Not whether a pathway is fast or slow, but whether there is room for it to switch when switching is needed.

The five sections above may look like separate observations. They point at one conclusion.

What the genotype sets is a substrate, not a conclusion. That substrate carries meaning only inside a pathway, and which step is rate-limiting only becomes visible once the pathway is laid out. Inputs from the environment layer on top of the pathway, and beyond those, the social arrangements a person lives in operate as part of their cognition. And what matters is not which state they are in, but whether they can move.

There are three reasons I do not diagnose.

The first is a line that cannot be moved. I am not a physician. Under Japanese law, diagnosis is reserved to licensed physicians, and that boundary is not mine to cross.

The second is that even without that line, the path traced above does not add up to naming where an individual is headed. The more layers stack up, the thinner the grounds for deciding an outcome from any one of them. A sentence of the form “you are prone to X” compresses all five of those layers into a single conclusion.

The third sits a little further back. Information is itself an input to the body.

A sentence like “your risk for this is high” rewrites the predictions a person's body makes about its own sensations. Change the prediction and the same signal starts to carry a different meaning. This is not a matter of attitude; it is a phenomenon that can be described as a pathway. Like sound and light, language is one of the doors.

Genetic results are heavy information for the person receiving them. Handled carelessly, the reading itself can do harm.

So what I can hand over is this: the fact of what your data holds and how it is structured, and how to read it. What you make of it beyond that is yours. If you have concerns about your health, please consult a medical institution, whatever the reading shows.