From the bottom. Study microbe brains. Learn to see inputs, outputs and data flow. Stay away from AI standard stuff.
Brains are the topic of study. They scale up, but cannot be torn down.
Here is a data flow.
Nature -> sensors -> brain -> motors -> nature
This is the loop.
Sensors read nature and write abstract data.
The brain reads data, does a function on it, and writes the result.
motors read abstract data, add units and move nature.
This is where it starts.