I enjoy these hypothetical scenarios.
I am glad we have widened this discussion to include more groups, too.
Picking up on Barracuda's "spark" notion, you might as well ask why
the wheel WAS invented somewhere at a particular time, as to wonder why
somebody did not invent it.
It is just as logical to say that the Egyptians or Sumerians were curiously
intelligent and creative, as to say that other groups were curiously not so. Somebody had to be first...and the others were therefore 2nd, third, fourth, etc.
...On the other hand, I wonder about our contemporary world....why is prosperity so elusive in certain areas? You can talk about geopolitics, but
there are other factors as well, such as culture. I started a thread about
aborigines somewhile back,but no one was interested. One of the things I learned was that the aborigines find modern technology, lifestyle, etc,
completely abhorrent and aberrant.
The deeper you go, the higher you fly.