@ReggieHere @deshipu @junesim63 @ainmosni - some say it started with raising grain: the elites get slaves or paid laborers to grow grain, store the surplus, use it to feed armies, etc.
Interestingly the storage of grain is also when cats started hanging out with humans. So it's not all bad.
Yes, the advent of agriculture and stored surpluses seems to be the consensus here. Prior to that people would have lived more nomadic lives and it would have been unlikely that anyone could 'farm' anyone else's production.
Absolutely. Society gradually coalesced as occasional societies became more permanent, but anthropologists place the earliest settlements at around 25000 BC while humans have been around for several hundred thousand years (give a millennia or two either way).
Whether those early societies operated according to a system of theft, slavery and forced labour, social credit, or a combination of them all is anyone's guess.
It's hard to believe that those things didn't exist, or that tribes wouldn't subjugate others when they had the chance, but if the global human population in 10000BC was roughly half of the population of modern day London, it might have been tricky to find people to subjugate.