Except that the methodology has improved a bit over “Og sick. Give stinky weed. If Og not die, medicine!”
Just for clarification: the four humors are choler, dolor, rubor and Good.
I apologize to all for losing my temper yet again. Without justifying it, let me explain it.
We start with:
The actual OP, ignoring its title, doesn’t mention “humors.” Instead it emphasizes “we all think of ancient medicine as complete quackery.” I knew this to be quite false, yet other Dopers tried to outdo themselves: “It was stupidity!” “No it was ignorance!!” “It was stupidity AND ignorance!!!”
I felt that injecting a different perspective was appropriate and did so. I should have written “gross anatomy” instead of “anatomy” but it didn’t seem a leap to assume Dopers understood that microscopes were not used before they were invented.
I took subsequent criticism too personally and responded in kind.
Sorry.
This advice mostly applies to colds and related self-limited infections. It’s not so good for, say, congestive heart failure. 
A major problem with “ancient” medicine was the frequency with which disease was treated with actively harmful interventions (bleeding, primitive surgeries and so on) instead of following the “first, do no harm” principle. Hippocrates had some good ideas, even though he was a Hippocratic oaf on other matters.
I have mostly addressed the meme that “if these treatments existed for so many years, there must have been something to them” - which has amply been demonstrated to be a fallacy, despite the fact that useful nuggets have occasionally turned up in what is otherwise a mountain of ludicrous, irrelevant and outmoded shit.*
*speaking of memes, there’s something to be said for the one that goes something like “50% of today’s medical knowledge will be obsolete in ten years” (or 20 years, or whatever). Consider then what percentage of ancient medicine is still viable today.
If it were just luck, then there would be no point in studying medical practices in Amazonia or such things, since you’d be equally likely to find a plant that says, lower fever, by picking an herb at random in the forest and by trying those traditionnally used to lower fever.
And medical practices in Amazonia are nowadays closely studied in search for new useful molecules.
I would find extremely surprising that people wouldn’t have figured out, by trial and error, a large number of actually useful plants. They have figured out tons of things that were much less obvious. For instance, the process to obtain the purple dye from shells was ludicrously long and complicated, including fishing them at a specific time, removal of a gland, salting, drying them under the sun for a specific duration, boiling in specific ways for weeks, and so on…However, it was mastered during the antiquity. By comparison, figuring out that wounds heal better when you apply some basic product or plant is quite easy.
The process for making tapioca in complicated, too. But neither process is confounded by the indredients sometimes spontaneously coming together to make purple dye or tapioca no matter what process you’re trying. The body, on the other hand, can often get well, or go into remission, on it’s own. That is a BIG complicating factor.
Let’s simplify that argument. Let’s take rattlesnake bites in the Old West. There were hundreds of snakebite cures, with thousands of testimonials backing them up. However, humans are not a rattlesnake’s regular prey. They’re striking in defense. Sometimes they inject a significant amount of poison. Sometimes they inject just a little poison. And sometimes they inject no poison at all.
They need their poison to take down prey and it’s better for them if they don’t waste it on something that they can’t swallow. This is a complicating factor. Person A gets snakebit. He pours whiskey on the bite and takes a strong nip himself. Or he spits tobacco onto the bite. Or he cuts it open and does both. And he’s fine as long as he doesn’t absorb enough nicotine to kill him.
You can talk all you want about snakes sometimes not injecting poison, he has officially saved himself from a rattlesnake bite. He will spread the story. If there are enough local snakebites that seem to respond to the treatment, the treatment can become established, become traditional, even though it has absolutely no effect.
I wouldn’t call unanalysed trial and error utterly useless, but double blind studies are still the gold standard. Trial and error practices will result in the collection of a list of local materials that have some effect on the human body. Materials that cause numbness, tingling, dilation of the eyes, stimulation, etc. feel like they’re doing something. A researcher studying that list will be more likely to find something useful than a researcher starting from scratch with everything in the area.
Anyway, it’s not that the folks using trial and error or any older medical theories were dumb. It’s that the body’s ability to heal complicates trials. (I can remember my grandmother insisting that putting cold water or ice on mild burns will ‘drive the heat in’ and insisting on using room temperature butter instead. The burns healed.)
I don’t think anyone in the thread is arguing against the scientific method. :smack: We just point out that wholesale deprecation of traditional remedies is absurd.
And note that the problems you describe are manifested today, albeit not in well-designed “blind” studies. A woman has a small breast tumor, has a mastectomy, and doesn’t develop cancer. Would the woman have developed cancer without the surgery? Probably not.
I don’t see a wholesale deprecation of traditional remedies. I see a reaction to “it was used for a long time so it has to work.” Not the same thing at all.
Digitalis was derived from foxglove. Cool. Well done. Let’s get the dosage established.
There were thousands of snakebite remedies, though, dozens of which became traditional, and not one of them was effective against snakebite. For snakebite you need antivenin.
Just because it’s traditional, doesn’t mean that it works, or must work a little. That’s not the way human minds and treatment evaluations operate. We learned that the hard way and don’t want to lose track of that bit of information. It’s an important bit.
How closely was the OP meaning to stay to the four humors? Because that has been debunked up, down, and sideways. If that’s the “ancient methods” under consideration, there’s no doubt that it was meaningless at a theoretical level and unlikely to be of use at a practical level.
(It’s fun to play with at a dietetic level, though.)