Trial and error?

Bingo. We only know which mushrooms that are tasty or give us a fun time because a lot of people died finding out.

There's also cheating : isn't coffee bean edibility observed from goats? essentially outsourced trial and error is a thing too.

Which is exactly what we do with lab mice.

Not only that. A lot of mushrooms can be eaten in small doses but will cause things like stomach upset well before death. I'd bet we as a species would quickly test mushrooms this way without dieing.

At some period in our evolution, it gave us pre-dispositions to certain tastes. Like our fondness for sweet & salty is universal.

We have systematized these pursuits. Even before modern science, language could be used to crudely pool together individual trial and error as a huge force multiplier.

I’ve often wondered how the heck did people invent soap? What made them think mix ashes and fat together and use the result to make stuff cleaner? (And that’s ignoring the fact that at a molecular level, soap is pretty amazing in and of itself.)

roasting meat, fat dripping in the ashes. At some point someone wondered the next day "hm, that's funny"

Some tribes have a drug with sophisticated preparation steps from multiple plants and they claim the plants spoke to them about their ability. Carrots were pencil thin woody roots, almonds were fatal, bananas were half rock hard seeds, rice was just another grass, wolves were skittish and bare their teeth at humans. How did ancient humans see potential in them?

I would imagine that a lot of wild plants that we regard as not particularly edible can look much more enticing when that's basically your only choice of food.

As far as wolves, it's still an open question as to how much they "self-domesticated" before humans noticed and started working from the other end. Seeing how human encampments would produce delicious food scraps in refuse (and still do, just ask any black bear!), it stands to reason that some animals would try to cash in on that opportunity. Then you have a selection process whereby the ones that are too skittish would not even bother, and the ones that are too aggressive would be chased away or worse.

The book "Guns Germs and Steel" has some good answers to that question.