Surprised the Terence McKenna admitted that Food of the Gods (which introduced the “Stoned Ape Theory”) was consciously a work of propaganda. This doesn’t mean he didn’t believe the theory, it just confirms that the main intention of the work was to change public opinion on drugs:

“Since I feel pretty much around friends and fringies here, it doesn’t trouble me to confess … FOOD OF THE GODS, I conceived of as an intellectual Trojan horse. Written as though it were a scientific study, citations to impossible-to-find books and so forth … simply to ‘assuage’ academic anthropologists. THE IDEA IS – to leave this thing on their doorstep; rather like an abandoned baby, or Trojan horse” (SOURCE)

“I felt if I could change the frame of the argument and get drugs insinuated into a scenario of human origins, then I would cast doubt on the whole paradigm of Western Civilization, in the same way that realizing that we came from monkeys did a great deal to re-set the dials in the 19th Century Victorian mind. If you could convince people that drugs were responsible for the emergence of large brain size and language, then you could completely re-cast the argument from: "Drugs are alien, invasive and distorting to human nature" to: "Drugs are natural, ancient and responsible for human nature." So it was consciously propaganda, although I believe all that and I believe it's going to be hard to knock down.”
“The target audience will be the converted first of all, but my hope is that the engines of public relations and publicity will move it much more into the mainstream. The 18-25 year old group that is drug-friendly but has no rationale except that it's a good time. This book is what I want every co-ed next Fall to be carrying to Anthro 101 to beard the professor with. You've heard me talk about meme wars, and how, if we could have a level playing field, these ideas would do very well. The theory I'm putting forth—to disprove it you would have to get your feet wet and get stoned. Anybody who doesn't want to do that should rule themselves off the case. So that presents academic types with a real problem.”

Food of the Gods

How to Change Your Mind: What the New Science of Psychedelics Teaches Us About Consciousness, Dying, Addiction, Depression, and Transcendence