Exactly @markush! Just like a key fitting into a lock and then being able to open the door and walk right in like they own the place. Then, they start to clean house and restore order, again like they own the place. There isn't any other plant that I know of that uses the endocannabiniod system. I have read that when you have traditional Chinese acupuncture, it stimulates the cb2 receptors with the insertion of acupuncture needles....that would be the only other thing that would come close...other than some other foods that can prime the receptor sites and get them ready to bind with the cannabinoids found in cannabis. If you eat these foods about 45 minutes before smoking, eating or vapourizing ,they will actually heighten the effects of cannabis. (Basil, hops, mango, lemongrass, hemp seeds and hemp oil are a few of these foods.)
At the end of the day the herb came first and it fits us biologically just like a glove. ;)