First off, it sucks what happened to this thread in the last few pages. Glad to see it coming back on this page.
Secondly, I have always felt the the presence of this shared chemistry begs the question, did one species evolve in response to the other? Well, to find the answer, we might look at what other animals can use cannabis? Anyone ever get their dog high? I think the "evolve alongside" theory is a close miss. I think a common ancestor, with cannabis the remaining species miht be closer. Hops, the only other genus in this family, is also psychoactive, but really is only a sedative, lacking the psychedelic effects. Hops has other physiological effects, though, affecting digestion and other systems (liver, kidneys, reproductive).
Thirdly, as an herbalist, I occasionally find uses for this plant. The old docs (the Eclectics, Physiomedicalists, and the early Homeopaths) up 'til the 1930s used cannabis mostly for sleep related issues. Bad dreams, in particular, is a primary indication. This plant comes to mind for me whenever bad dreams accompany the problem for which my client is seeking my help. It does not matter what the problem is, if they have nightmares and are down with it, Cann. usually ends up in their formula. The indications surrounding the eyes are also fairly old. Dating to the middle ages, at least.
I have often wondered if the association with the eyes came from its psychedelic effects. Ever take a lot and chill alone in a quiet, dark room, as Terence McKenna suggests? Well, it's a VERY different experience... much more psychedelic.
Another thing I find interesting is the difference the route of administration, as well as the preparation method, can have on the effects. Smoking is pretty familiar to most folks, and many have had the slower, "shroomier" experience of brownies or cookies. Tincture, though, is much more sedative and anodyne (pain-killing). Heating the raw material before tincturing, increases anti-inflammatory and anodyne properties while rducing the "stoniness" by changing the balance of THC and other cannabinoids.
Fascinating plant, really. It certainly is on my top ten medicinals, but is not in my list of most commonly used ones.
Anyway, glad to see the real conversation coming back!