What's the world's oldest civilization?

[wnylib]

10. I agree about irrigation as a marker

of civilization.

I also question how civilization is defined. The Inca, for example, never developed a writing system, but are often referred to as a civilization and had a unique record keeping system.

Coincidentally, the Iroquois in what is now NY, also used a knotting system of shell strings for records and contracts between individuals, used woven shell belts depicting symbols as treaties, and had a sophisticated governing system with an oral "constitution." They had semi domesticated animals, horticulture, semi permanent towns and villages, a massive trade network, but were not a civilization. They had no permanent structures or monuments and no urban centers.

Many societies have had impressive social/political structures or material structures without reaching a state that we would call civilization. Others, like the Aztecs were definitely civilizations, but resolved some things in unique ways.