stupid 5 minute edit system
captain hanks your cannabinoid receptors were active and awoken from your first breath. they're used for other things, not marijuana exclusively. they are called endocannabinoids, anandamide, and 2-arachidonylglycerol, and they are generated in your body at a constant and consistent rate.
cannabis sativa will bind itself in the same way that these enzymes bind themselves to the cannabinoid receptor, and that is proven, so therefore there is no way that the brain isn't 'prepared' for cannabis sativa