Ancient Civilizations and their Demise

My premise is that preclude to their own demise, all ancient civilizations engaged in Wars of Attrition.

That premise is valid, even though we have not entered the World War III yet, all the indications are we are ready for one.

Lack of diplomacy is the Cardinal sign of War of Attrition.
Diplomacy takes a second fiddle at the time of war.

I leave it at that.

Other reasons without order of merit are;

1. Communicable diseases.
2. Famine
3. Catastrophe due to fire, floods, extremes of weather, volcano eruptions.
4. Meteorite hits. 
5. Alien wars fought on this planet where fleeing aliens wers pursued to extinction 

What happened to;
1. Sumerians
2. Incas
3. Ancient Egyptians
4. Ancient Pacific Islanders
5. Harindajaro Harrappans