You are absolutely right - the underlying premise is that "fungi is intelligent, and it passes some of that intelligence to the apes, when consumed". This makes no sense. Just came to mind since McKenna also rants about fungi networks being the largest intelligent being on the planet, etc.

McKenna said some weird stuff, but the stoned ape theory is probably his most believable idea.

Intelligence and creativity didn’t arise because protohumans became fungal hybrids, but rather the psychedelic mushrooms not only provided sustainance, but also provided behavioral changes like better visual acuity (I believe this claim is proven), sexual arrousal. This mean mushroom eaters were more likely to reproduce. As a sideffect, the psyliopsybin either promoted neural placticity, or novel wirings.

Protohumans that didn’t eat mushrooms died out, and the most successful eaters were the most clever protohumans. (Perhaps behavior became the dominate sexual selection criteria, rather than say meer physical features.)

He says a lot of other weird stuff like, mushrooms are from space, are conscious, or maybe are communication devices, or maybe prerecorded messages from alien “self transforming machine elves”, or maybe they are the elves?

Oh well. All will become clear when universe hits maximum novelty in 2012.

I wouldn't state "makes no sense" about something like that. For example, in sci-fi terms, psychedelic molecules could be akin to a 'protomolecule' that attaches to self-replicating entities and attempts to induce ??consciousness??

We don't know any of this for sure.