Yeah, its not like, when encountering a new food that a) they have to consume large enough quantities of it to be fatal b) that there are not proxies (e.g. tast

Yeah, its not like, when encountering a new food that a) they have to consume large enough quantities of it to be fatal b) that there are not proxies (e.g. taste) or testing protocols (does it irritate the lips) that can provide clues to its toxicity, or c) relevant similarities to other known species that would suggest its probable toxicity or d) there are not existing observations of wildlife doing some sort of processing that reduce toxicity of said species. All of these also provide means of refining food processing techniques to reduce toxicity. If after cooking, the root is less irritating to the gums, or tastes less bitter, then maybe cooking it some more will do better.