Civilization has also been defined by [[Clyde Kluckhohn]] as having "three essential criteria for civilization: towns containing more than 5000 people, writing, and monumental ceremonial centers".<ref>http://www.historyguide.org/ancient/lecture1b.html</ref> | Civilization has also been defined by [[Clyde Kluckhohn]] as having "three essential criteria for civilization: towns containing more than 5000 people, writing, and monumental ceremonial centers".<ref>http://www.historyguide.org/ancient/lecture1b.html</ref> |