What makes war a way of life during the ancient period?

Human beings are competitive animals. We evolved a ruthless competitive edge which allowed us to gain dominance over other animals and this inbuilt drive continued against other humans: in early societies there was competition for resources - farmland in particular, so land piracy was basic as populations increased. Nomads pillaged agriculturists, who defended themselves. Agriculturists fought each other over property disputes or mineral ownership. As trade grew, there were disputes over that too. Inherent in population surplus was the inability to continue dividing small farms amongst several sons. One solution was sending out colonies of surplus people. Another was to capture others' land. And in the process of warfare there were losses of young men which helped the problem. Nothing much has changed, other than we now have competitive team sports where some of the inbuilt aggression is spent in either participation or watching, however even here excessive sports violence is not absent.