On the Origin of Modern Mentalities

The invention here is somewhat abstruse. Please read carefully before giving this the MFD for not actually being an invention. Thank you.

First, a Mystery:
According to the paleo-archeological record, about 50-70 thousand years ago, "socially significant" artifacts began to appear, such as flutes and decorated (with something like embossings) pottery, and painting. Prior to that, the human species existed in "anatomically modern form", according to the fossil record, for as much as 150 thousand years.

Well, if we have been physically modern for about 200 thousand years, why have we been mentally modern for only 60-or-so thousand years? That's the mystery.

At least one existing proposed explanation involves a mutation with respect to human brainpower, which is something that PROBABLY would not be able to survive in the fossil record (there's a small SMALL chance of some surviving DNA getting found for testing, but even it it exists, it must be found before that idea can be tested).

This Idea proposes a different solution to the mystery, and a much simpler way to test it.

So, now to piece together some relevant facts:
The explanation begins with observations of rare cases of human children being raised by animals, and which are generally called "feral children". They simply cannot be taught enough to become ordinary members of society. Key brain elements either never grew, during earliest childhood, or atrophied.

It is known that for a child to achieve full mental development, such as is normal for most children, an environment of intense mental stimulation is required, for several of the earliest years of growth. Feral children did not have such an environment.

And neither did ANY of the original humans, 200,000 years ago. All humans at that time must have qualified as "feral". However, they still had significant intelligence and were able to create some basic things like stone tools. (Even today, every human baby is "feral", and would remain so if deprived of sufficient mental stimulation.)

Likely they also created descriptive words, even if they did not create an actual language. As the millennia passed by, more and more total things got created, and needed to be taught to their children, although all humans were still "feral".

But, about 50-70 thousand years ago, the total amount of mental stimulation given to the children of that era reached a kind of "critical mass", and the result was, quite simply, that those children became the first mentally modern humans.

As actual evidence in support of how mental stimulation can achieve a degree of mental modern-ness, even for a non-human animal, consider the case of "Koko the gorilla" (see link). Her abilities are limited because her total brainpower, compared to humans, is limited. But she has ENOUGH brainpower, as did all humans for more than a hundred thousand years. It merely needed enough early-life stimulation!

Finally, the Test
Since it would be considered unethical to take human babies and deliberately deprive them of different amounts of exposure to mental stimulation, to discover which ones become "feral children", the opposite approach is recommended.

Take a bunch of gorilla babies, and raise them like Koko was raised, but for different lengths of time, so that some of them do not turn out like Koko (they remain feral), while others do turn out like Koko. Carefully keep track of all the data that these gorilla babies are being exposed to. We want to find the "critical data mass" value, the amount of data that triggers Modern Mentality.