Possible causes of early human history mass violence and especially war?

A genetic mutation or mutations

Issues around sewage in cities

Plotting abilities of city leaders changed

Fears based on conflict with animals echoed into human relationships

Climate change and earthquakes as a cause

Advances in weaponry especially the Age of Copper

The development of boats and eventually fleets

The domestication of dogs which were then much more wild

Religion being very primitive in certain regions

Powerful people's like the Egyptians and perhaps Atlantians causing tension and envy

The insanity of despotic rulers who become corrupted by their own power

Fights over natural resources especially water and places better for agriculture

And lastly the Egyptians lost their strong interest in creativity and focused instead on giant pyramids