This is true, but only for the past 6 thousand years or so. For 97% of human history, this was not the case. Paleolithic hunter-gatherer tribes used enforced egalitarianism as a prime survival strategy and even early cities that had kings, mayors, etc., were primarily run on a day to day basis by neighborhood councils that operated by consensus and the leader's role was largely ceremonial. In many Native American tribes, chiefs essentially had only power that their subjects agreed to and they had no power to impose rules or punish anyone. For more on this, read the book The Dawn of Everything which goes into the myriad examples and an in depth look at this phenomenon.
In general, the advent of agriculture around 12K years ago is looked at as the time when egalitarianism began to be wiped out by dominance based hierarchies, but there were proto-agricultural cities like Çatalhöyük that were intentionally egalitarian for thousands of years.
And as noted above, other early cities and civilizations functioned with little hierarchy that was enforced by coercion, intimidation or violence from "above" until that began to shift around 5-6k years ago. The earliest archeological evidence of any kind of mass violence comes from 13,000 years ago, and most of it comes from 8,000 years ago and more recently. Many anthropologists believe that the human ability to intentionally transcend our primate ancestors dominance hierarchies was a central element of our evolution.
Here's some links to pieces that I've written about all of this although The Dawn of Everything has rounded out my prior reading and research and once I get around to it, I'm planning to write something that explains how the agricultural revolution alone was not the only factor or in some cases, the main factor that signaled a shift to male-dominated dominance hierarchies (e.g., patriarchy).
I appreciate you asking for clarification and more information. Modern hunter-gatherer tribes retain a lot of this same fierce egalitarianism that stems from their dual belief in individuality (not being told what to do by others) as well as their buy in to the welfare of the entire tribe, not just for themselves or their families. This level of cooperative behavior is absolutely a way to support both the safety and well-being of the group, which in turn, is beneficial to the individual.
Primatologist Frans de Waal explains it this way, “Destabilization of the social resource network decreases group stability and efficiency and lowers the average fitness benefit derived from cooperation. When group stability is important for individual advantage, selection will favor active peacemaking and cooperation in our closest relatives and ourselves.”
And here is another relevant quote about modern H/G tribes: In each of these societies, the dominant cultural ethos was one that emphasized individual autonomy, non-directive childrearing methods, nonviolence, sharing, cooperation, and consensual decision-making. Their core value, which underlay all of the rest, was that of the equality of individuals. Source
Let me know if you have further questions.
