>Apparently many North American indian cultures had no word/concept for TIME. ...
>But I somehow see a concept of TIME as critical for the kind of stuff you're talking about. I think that recognizing time and then doing things to accommodate/abbreviate/extend time is the important distinction.

You're referring to the Hopi Indians, their concept of time made famous thanks to the Whorf Hypothesis.

http://www.humanevolution.net/a/hopi.html

That is interesting, and I actually looked into when I was starting to investigate how my intuition towards time differed from the standard dimensional view our society inherited from the Greeks.

But that's not quite relevant to what I'm refering to as the Cultural Explosion. Here's the question (paraphrased from another source):

more than 2,000,000 years between Advanced Australopithecus and Neanderthal, and the tools of these two groups—sharp stones—were virtually alike—and the two groups as they are believed to have looked—were hardly distinguishable.

the suddenly, some 35,000 years ago homo sapiens appeared and swept neanderthals off the map.

these homo sapiens—cro-magnons—were the creators of cave art—cavemen.
they roamed freely, they knew how to build shelters, and for millions of years Man’s tools had been stones of useful shape—yet cro-magnons made specialized tools and weapons of wood and bone.

so, how is it that after 2,000,000 years of being naked apes, without much change, did we suddenly become creatures that made art and weapons?

The explosion in question took place approximately 35,000 years ago. If I am not mistaken, native Americans only migrated over the Bering Strait 20,000 years ago, so they would not be isolated from what we're talking about.