Regarding that quote from Carl Sagan above: Although I have great respect for Carl Sagan, I want to caution against certain possible misinterpretations of what he was saying.

(I just spent several minutes searching for that quote in my copy of "The Demon-Haunted World" and failed to find it. I don't doubt the quote is real; I just wanted to see it in context.)

Without a quote of my own, I can't prove this, but I THINK Sagan was arguing in favor of "min[ing] the treasures in such folk knowledge" and then subjecting that knowledge to rigorous scientific testing. I don't think he would ever advocate using any herbs just because native healers say it works for them.

There are a lot of shortcomings of accepting "knowledge" that is only tested informally. For one thing, native people are not likely to discover that drinking (or smoking) a certain herb when you're 20 can cause cancer when you're 50. In some of those cultures, it's pretty rare for anyone to live to age 50. For another thing, certain herbs may be valued only because they're better than nothing, and we have better alternatives.

And I think most "alternative healers" wouldn't know a double-blind test if it bit them in the ass.