I've heard this said .. admittedly, deep within the bowels of many a coffeeshop .. of marijuana.<p>Basically, weed rewards us for its continued safe domestication.<p>Try as I might, I cannot find a way to disprove this theory. The more I test it, the more it seems absolutely correct.<p>The same of course, is true of coffee and tobacco, albeit the means of domestication differ in magnitude and effect in each case.<p>The jury is still out on Triffids, however.