Why do people think we don't know anything about cannabis? We don't know a lot about cannabinoids, et al, and how they function within the human body; however, we're talking about a crop which was MANDITORY to produce in the US until just over 50 years ago, with a 12,000 year history of cultivation prior.
Moreover, you know how THC levels have gotten so much higher? Those numbers are from the Fed, and the largest factor in the increase of THC by weight is that people started trimming bud. That right there is a massive sample size, thus a mountain of evidence that you are wrong.
But hey, at least we're not talking about smoking roots, eh? Because I've seen that too. :/