Prehistoric pharmaceutical R & D

Both betel nut and coca leaf are used with lime, presumably taken from the ashes of a burning shell midden. Trade for these items often initiated contacts between far-apart groups (coca-growing highlanders traded for coastal-dwelling lime barons). I have never seen any explanation for the [presumably] trial-and-error experimentation that led up to this.

"Hey Og ! This nut tasted terrible, has no effect, animals don't eat it. Let's mix it with something and see if it can be used ?""OK, Grog, let's try it with fruit bat droppings - yecch ! with burnt fruit bat droppings - yecch ! with [a multitude of plants] - ptui !, ad infinitum until you get to oysters, burnt oysters, oyster shells and finally burnt oyster shell.

Seems odd that two things you would avoid putting in your mouth separately, for either taste or effect, should be tested together - and then two things that aren't typically found together at that.

Any thoughts, other than eons of trial & error ? (Von Daniken theorists need not apply.)

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"Proverbs for Paranoids, 1: You may never get to touch the Master, but you can tickle his creatures."
- T.Pynchon, [i]Gravity's Rainbow.

Mad scientist - Igor pass me that bottle.

Igor - Yes master, oops.

Mad scientist - You idiot you spilled your cocco into my oyster shells.

Igor - Hmmmm tastes ok to me.

A) tpyo'd my UBB codes, sorry...

B) Thanks Mac, a better image, and the answer I deserved for that question.

C) Fine-tuning the question:

In neither the West Pacific (betel nut chewers) nor in the Andes (coca aficionados) do I recall any other medical/gastronomic uses for lime (construction or art, maybe)- in addition to the unlikely natural co-location of a source of lime with the betel or coca.

Not only do you get the Mad Dr. - Igor scenario, but the additional twist of a Mad Dr. who recruited an alien, I meant foreigner, to help test with foreign materials that serve no other similar purpose.

Alchemists mixed all kinda stuff looking for the "Philosopher's stone", but had a specific goal - gold - in mind. As opposed to trying to make use of one or the other, otherwise uninteresting, product, sorta like producing a Yanni rap album.

Either there are other traditional uses for lime, recognizing the chemical reaction, or Doc & Igor beat some unholy odds.

Still confused.

What does the lime do? Does it, perhaps, neutralize the acid in the leaves? (Is it safe to assume you're talking about the sort of lime that's white and powdery, as opposed to round and green?)
Side note that may or may not be enlightening: Native Americans mixed ashes with their acorns to make them edible. Normally acorns are too acidic (tannic acid) to eat.

Coca leaves would also numb the mouth which may make it easier to chew other things.

Yup, lime the white powder. In both cases, the addition of the lime "activates" the desired pharmaceutical effect - the coca leaves wouldn't numb your mouth unless the alkaloids were "freed" up, and the betel nut has little effect without it, too.

Good example with acorns, however acorns and ash (at the remains of a fire) would be a likely accidental discovery (the co-location issue). Also, animals eat acorns, which would not have escaped the notice of a hungry band of travellers.