However listening to it's originator Terence McKenna explain the stoned ape theory while intoxicated on the correct substances is a very fun experience.

The author must have wrote that book when he was high on shrooms.

An animal in the wild will try to eat everything and learn through trial and error what is good to eat and what isn’t. Selection might even lead to behavioral changes that naturally predispose one to one substance over another. I don’t see why humans would be any different.

Trial and error? I think most animals have an instinct of what they should eat when. I think humans have that too, but kind of forgot about it, or at least we are out of touch with these things and mostly judge intellectually.

For many animals that instinct is to chew something and either swallow or spit it out. See a tiger shark. They basically probe the entire environment through constant trial and error. Bite it all should a small portion bleed, they have concluded.