What would C.S. Peirce say about Ron Unz’s IQ essay? Gene Callahan notes that IQ exams are more apt to test familiarity with symbolic signifiers — in which one thing represents another by convention — than indexical signifiers that “point” to their meaning. And different kinds of signifiers may predominate in different environments:
It seems plausible to me that people who live ‘close to the land’ — farmers, hunters, gatherers, fishermen, and so on — are going to be very keenly interested in indexical signs: the snapped twig that signifies the recent passing of a deer, the gulls circling that mean a school of fish is nearby, the withered leaves that indicate a fungus is attacking one’s crop.
City dwellers, meanwhile, live in a largely human-constructed world, and deal much more extensively with symbols, or conventional signs: billboards, shop signs, traffic signals, walk lights, newspapers, parking instructions, eviction notices, and the general omnipresence of human conversation.
I’d add that even city life may now be more symbol-oriented, in the broadest sense, than in generations past.
Cascade Joe 
This line of reasoning would make perfect sense if one group had evolved in cities and the others evolved “Close to the ground.”
But we are all descendants of populations living close to the ground while only some of us are the descendants of those who invented agriculture, written language and cities.