Indeed, anarchy was the default state of human nature until communities reached Dunbar's number, i.e. around 150 people. Then, they did invent civilization for a reason!
What we are talking here is a community of adult people.
People might think the British were not brutal with their own people, but if you read up on the Clearances, you’d know they valued people less than sheep.
Don't fool yourself! The niceties of modern times require a critic mass that is orders of magnitude larger than what anarchism can cope with.