Inherited complex knowledge and human society did not form until a few thousand years agoI think you are vastly underestimating millions of years to the contrary.
Tribal living had complex knowledge. Just how to make a bow, a spear, preserve food, build shelter, cloth themselves, hunt, harvest crops, treat many illnesses with local plants, coupled with the fact that it all had to be learned in great detail, first hand, for there was only oral history.
Even things such as "where are the animals" and "where are the apples" is complex, when drought, inclement weather, might cause local shortage, and traveling as the grandparent remembers "when I was young" for some alternate food means everything.
There are plants which taste like crap, but will keep you alive, but that sort of knowledge is lost unless you have Google (grandparents) around.
Have you looked at how corn meal is prepared in native cultures? I can't even imagine how many centuries, or thousands of years of trial and error that took, to make it edible.
https://en.m.wikipedia.org/wiki/Nixtamalization
What about our wormy Guinea friend?
https://www.britannica.com/science/guinea-worm-disease
If you yank this worm out, it typically rups in half. The remainder rots inside your flesh, usually killing you without modern medical care
Who retains that knowledge, for when an outbreak hits the tribe?
Who lives long enough, to notice over time (decades of adult life) what might cause the parasite.
Without paper, without Google, without written language, everything learned must be transferred to the next generation of grandparents. By having free time, by talking.
And grandparents can do many tasks which active hunters and gatherers cannot, for they have no time!
Repairing and maintaining weapons, fixing clothing, transport vessles, preparing food (which can take hours and hours), and so on.