[yahwrong]

> So naturally if you consider lack of exercise as the natural state of humans, sure it will appear physical activity improve brain function.

I think not wanting to do more work or exert more energy than needed is the natural state of all of nature. Nothing does anything more than what requires the least amount of energy. However since humans are at least somewhat self aware they can 'determine' regular exercise is ultimately less annoying or less energy than being obese, depressed, and with likely more medical problems.