Some anarchists, feminists and anthropologist would say the first long term hierarchy was patriarchy. When men established positions of power (priest, warrior) that fit their interests well, they changed the societal structure from matricentric to patriarchal and started to establish the state.

Öcalan (not a scientist) dates this in his work Beyond State, Power, and Violence at around 6 thousand years ago for the area of the so calles Middle East.

Dont know how others see this but there probably is not a scientific or anarchist consensus on the topic.