Ardreys' Territorial Imperative explains it all.

https://www.thriftbooks.com/w/the-territorial-imperative-a-personal-inquiry-into-the-animal-origins-of-property-and-nations-kodansha-globe_robert-ardrey/1114432/item/39488871/?mkwid=%7cdc&pcrid=77447028765158&pkw=&pmt=be&slid=&product=39488871&plc=&pgrid=1239149900899965&ptaid=pla-4581046492312226&utm_source=bing&utm_medium=cpc&utm_campaign=Shopping+-+High+Vol+Backlist+-+Under+%2410&utm_term=&utm_content=%7cdc%7cpcrid%7c77447028765158%7cpkw%7c%7cpmt%7cbe%7cproduct%7c39488871%7cslid%7c%7cpgrid%7c1239149900899965%7cptaid%7cpla-4581046492312226%7c&msclkid=ef3761305d921c146ebd060ca70fc1ec#idiq=39488871&edition=35596301