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.)
“Proverbs for Paranoids, 1: You may never get to touch the Master, but you can tickle his creatures.”
- T.Pynchon, Gravity’s Rainbow.