An interesting concept. I believe I've come across a few allusions to it. Arthur Machen wrote a short story called "The Red Hand" that seemed to imply something like this very idea (and it should be remembered that fiction often functions as a outlet for occult teachings, and Arthur Machen was a member of the Golden Dawn).
>Cranial/ Brain Size of Homo Neanderthalensis
Many people are under the misconception that Homo neanderthal had a smaller brain than modern humans since they were not as evolved. But their brains were just as large as ours and often larger, proportional to their brawnier bodies. Homo neanderthal brain size was larger than the average modern human brain and averaged 1500 cubic centimetres and an average 3.3 lbs. This is to be expected, as Neanderthals were generally heavier and more muscular than modern humans. People that live in cold climates also tend to have larger brains than those living in warm climates
https://www.cobbresearchlab.com/issue-2-1/2015/12/24/average-cranium-brain-size-of-homo-neanderthalensis-vs-homo-sapiens
There is some evidence that "primitive" hominids were actually more intelligent that modern humans, and there seems to be a correlation between Neanderthal genetics and IQ in modern populations. I don't actually know much about the so-called "paleolithic deep state" but I want to find out more.