I think the Stoned Ape Hypothesis (sah) is reasonable within the context of a social lawlessness found in the state of nature. The chaos of the animal kingdom would permit the transgression of norms among primates, with little consequence, and it wouldn't matter as much for animals to be indulging in mind altering substances, if other needs were all essentially met by the surrounding environment.

Evolutionary theory is founded mostly on untouchable mechanics that operate at nearly geologic time scales, so we look, and we see slight incremental changes, and say to ourselves, yeah that holds up the rest.

But at it's core, the fundamental question is: Why did the human brain explode onto the scene? Why wasn't that change gradual? Why did it only happen once? Was there an accelerant in the mix?

To say that it happened fast is to speak in relative terms. It still would have happened across multiple generations, in movements of 10 and 20 years, according to sexual maturation. But to jump the rails, the change would have had to represent an ignition of sorts, to kick off a chain reaction that spreads outward from primary events, and is easily replicable crossing regional boundaries, once a successful game changer is cemented as viable.

The human brain isn't totally unique in it's structure, if you look at elephants and dolphins. But the relative brain size to body size ratio, as an emergent evolutionary trait, seems to be pretty unique.

Diet sounds like a plausible point of origin, when considering that the brain is a nutrition-greedy organ. So, the Stoned Ape Hypothesis is reasonable, in the sense that it layers nutritional augmentation on top of evolutionary theory. On the one hand, you still have evolutionary mechanics as the operating framework, but the dietary augmentation produces behavioral effects that change mating strategies.

So then, selection processes take over, and the successful live, and the others die. The successful produce alike offspring, and combinations of traits group together. But all clustered around this drug induced behavioral mess, where you find these apes getting into catnip and going nuts.

The idea is not without precedent. Consider the Greek Oracle, as a temple ventilated with toxic volcanic gases, acting as the mind altering substance. People willfully producing an altered state, by effectively huffing volatile, oxygen depriving vapors not unlike spray paint fumes, to gain insight and augment decision making.

Which brings us around to the crux of the idea. It should be possible to replicate the process, even at a small scale, by modeling the scenario with other animals. Usually mice have a short enough lifespan to push their genes around with careful engineering. So, what about talking mice that modify their environment? Could drugs and rampant sex make that happen in a time frame comparable to the fossile record for humans?

But geeze, talking mice that invent and implement conceptual ideas? What would we do with them, once they're here? What if they escape the lab? Would their population explode as an invasive species? Capable of direct lilliputian competition with humans?

Once the invasive species status is realized, all the rest fits into place. We wouldn't want to let the mice escape into the wild. So the only missing piece, regarding the mechanics of the idea, is the bridge in between dumb mice and smart mice.