Thanks for pointing this out; I've never heard that idea before.
But I don't think it holds water. The ability to talk and invent happens across our whole species regardless of recreational drug use. That means the explanations are to be found in genetics and evolution, not psychochemistry.
Could it be that the primitive humans that used these substances adapted better to their environment compared to their non-indulging peers, and we're more likely to be direct descendants of them?
Not saying you are wrong, or right, but rather that it would be naive to dismiss this idea based on some notion of genetics and evolution. At some point the choices we made as a species in the past comes directly into play with the natural evolution our genes and culture.
One of the more obvious ways in which drugs could have played a part in our evolution is, roughly stated, how the consumption of certain substances may have kept those individuals with more developed brains from going mad, or counteracted some of the disadvantages, allowing the trait to be passed on.
> That means the explanations are to be found in genetics and evolution, not psychochemistry.
Right, the point here is that perhaps the psychoactive substances aided our ancestors in making decisions or enlightening them(or straight up enhancing their senses) to withstand the test of evolution.
I'm not saying it gave them superpowers, but perhaps it enabled them to look at a particular challenge in a different perspective.
In fact, one of the data points that McKenna uses to base his theory on is that magic mushrooms increase visual acuity, making edges and outlines "stick out" more. This is a positive effect that could give some survival advantage to a primarily tree-dwelling creature that, due to desertification, must spend an increased amount of time on the savannah potentially being stalked by big cats, and could explain one reason why the apes would have sought them out.
It's a very interesting idea in which he invested a lot of time exploring. In the talk that I listened to, he opens by giving a disclaimer of sorts: he recognized that it's a far-out idea, but it is not an unsound one even though it lies pretty far away from the established narrative. He had a bunch of these "psychedelic ideas" and thought that it was important for people to keep coming up with them because they expand our understanding of what is possible. Sort of like psychedelics themselves, which is probably why he used the term.
But I don't think it holds water. The ability to talk and invent happens across our whole species regardless of recreational drug use. That means the explanations are to be found in genetics and evolution, not psychochemistry.