It begins with a garden or two. Once you have gardens, you have a resource that has the two most important characteristics anything can have with respect to human society. First, you can eat it. Second, your enemies can destroy it.
If you have just a few gardens and get your food somewhere else, no big deal. But back in the old days, and by “old days” I mean any time during the last several thousand years everywhere and anywhere that is not urbanized and has gardens, most people relied on their gardens. These gardens were maintained by families or small villages or occasionally larger cooperatives.
Since a garden can be destroyed by enemies, you have to have a way of defending the garden and everything else. So weapons, militarism, bellicosity, and all that become normal. Note that you could have a herd of beasts instead of a garden and something like this would still happen. Note that if among your beasts there are those you can mount, usually horses, then your weapons, militarism, bellicosity, and all that are now much taller and can run faster, so if you are the only ones with that setup you win.
This all leads eventually to an arms race that usually no one wins for too long. This is the Hobbesian world of Warre, where people are nasty brutish and short, or at least, their lives are. Eventually almost everyone in the world is doing this. Societies that resemble Medieval Europe’s Feudalism emerge wherever there is enough of this going on, which is why a French Knight and a Japanese Shogun and a Shona Chief are all kinda alike.
Then, something like climate change happens. Not the globally devastating climate change we are seeing today, but something likely more regional and not as severe, but that affects everyone’s gardens in roughly the same way. Over here you have famine more often, but over there you have higher productivity many years in a row. Maybe there is a three year long drought that causes mass migration, or maybe there is a summer with out a winter.
Or, if not climate change, population density increases too much and the gardens are not enough. So less than ideal land is planted, or more rapid turnover of cropping in a swidden system becomes normal, or something like that happens. People need to cooperate more to irrigate more, or to store or move around food more. The garden’s of the village become something slightly different.
In any event, the pot is stirred, but when you stir the Stone Soup of society over a large area, you don’t increase homogeneity like when you put all the different stuff in a blender to make a smoothy. Some stuff gets all mixed together evenly but other stuff clumps up and gets all goopy. The goopy parts, the clumps, those are Lords, or Bishops, or Shogan, or Overlords, or something that is bigger than in the old days. Instead of the guy in charge (and it will almost always be a guy because men can’t have babies and thus feel the need to take over everybody else’s junk all the time) being older and stronger and better connected than the other guys in a village, the guy in charge is the one with an extra 100 horses or a better blade or a clever strategy like stabbing the other guys up close instead of throwing something at them.
This is how you get a king.
Once you have one king, you’ll get other kings, or emperors, or whatever, until finally the only way somebody can be a lord or a chief is to suck up the king and that means fighting for the king. And taxes, you get them too. The gardens are now owned by the king, or if not, might as well be. The most convenient way to make this work, by the way, is to make sure that most people are not valid individuals, that they don’t have a place at the table. Those would be the slaves, or peasants, or whatever you want to call them.
Now there are kings or the equivalent everywhere, and some of them are relatively good and some are relatively bad. Badness may be enhanced by technology. Perhaps you’ve invented beer or wine but store it in lead casks so the privilaged few with the drink are more likely to be brain damaged. Or perhaps there is a mind-damaging venereal disease kings tend to get. Or perhaps just bad upbringing. Sometimes you get boy kings because the system of inheritance of power requires it, even though that is totally dumb. Boy kings can go either way. They tend to totally burn out or, alternatively, take over the world, eventually.
And you have kings with more power or with less power.
Eventually, in a region, something the size of a European Country or so, you get both a bad bad man as a king and a king that is very powerful all wrapped up in the same person. Everything that is bad about this sort of self organized system is now worse than it has ever been in anyone’s memory. It isn’t just the peasants taking it in the neck, but also, people in the middle who have power, lords and chiefs and such. Straws fall among the elite breaking one camel’s back after another.
This is when the people in the middle, who have now lost their power, insist on an agreement with the King that happens to benefit the peasants and slaves of the very distant future. That would be the Magna Carta, in the case of England. Other parts of the world have had other outcomes.
The BBC on the 800th anniversary of the Magna Carta, has produced a fun and interesting video exploring this history (though it starts later in time than the history I just outlined above.)