Starting from a very small population of cave people, as hominids expanded exponentially for thousands of years when everyone was still much more closely related no matter how far apart they were, migration pathways would not all have to remain open for tradition to be carried on to some extent.

I think it's also accepted that some cultures spent thousands of years with very little change compared to the climactic and geographic variations they endured.

Art periods are of couse referred to as "schools" and the most prominent way tradition is carried on by modern artists who intend to produce a work that will stand the test of time, is to use medias that are much closer to Rembrandt or Michaelangelo than what we see in the caves.

But not that different either.

Whatever was proven to last more than a few generations at the time.

IOW techniques proven over unknown generations of artists who came before, so much so that maintaining any knowledge on the subject required a degree of faith or superstition not less intense than efforts which preserved religious or cultural traditions, even of prehistoric humans.

Maybe for thousands of years.

It's not the Flintstones but it is just modern man in prehistoric times.

Artists who are contemporaries will need to develop a trend together in order for a school to form, and from what we see in recent centuries, a certain style often takes a while to catch on but also can last more than a generation even when there is only one progenitor as a seed.

Even though almost all art & science have always been lost without a trace.

The little bit that does stand the test of time and get preserved probably lasts much longer if it had been in development for more years before initial recognition.

And you've got to figure that schools of art come & go in much less rapid cycles the further back in time. But the materials that will last have evolved much less quickly.

The latest trends are still often depicted using inorganic pigments on canvas or carved in marble, and signed using the artist's name, styles can be wildly different but that part is exactly like it was done over the most recent centuries.

A recognized predecessor might have simply been inorganic pigment on a cave wall, signed with a hand stencil, when you're trying to paint a masterpiece that will stand the test of time. If nothing else had ever been proven this is what most would do.

And that tradition would likely have lasted orders of magnitude more generations when pop culture or art appreciation cycles were slower. Much slower in all probability, and probability can have some tall odds.

Like when there's not that many people in the world yet, most of them are going to be more similar than they are later.

Seems like the initial trend from earliest centuries could have actually lasted for earliest unfathomable millenia before any other school of art might have arose naturally as it was going to do anyway.

Could be all art everywhere started out always being signed with a hand stencil and it was so widespread and universal a trend it did not dissipate for tens of thousands of years. And it was everywhere, at home, at work, on billboards etc., you just couldn't get away from it, for like eons. It's been a while and it wouldn't be too surprising if the only thing preserved from way back then is in caves, and it could have been painted there intentionally for generations to enjoy into the unforseeable future, based on proven techniques from the unknowable past.