1) Individual brains don't evolve, evolution happens to the gene blueprint by which embryos make brains, and it is fixed before the new brain has had a single thought;
2) Your brain definitely doesn't understand how every other organ works in explicit detail; controlling organs only requires being part of a good enough feedback loop to have the organ mostly function; your brain understands your heart "at the molecular level" about as much fruitflies do.
2) Your brain definitely doesn't understand how every other organ works in explicit detail; controlling organs only requires being part of a good enough feedback loop to have the organ mostly function; your brain understands your heart "at the molecular level" about as much fruitflies do.