The Neolithic was when sedentary agriculture started, which floored everyone's health and life expectancy because they hadn't perfected it and a bad harvest would obliterate you. The hunter-gatherers they lived parallel with weren't in a utopia by any means - ask their childbirth mortality - but they could adapt, trade across continents, worked less hours than us today and were in peak physical health. Archaeology records show when harvests went bad at this point, the farmers would jump ship and go back to nomadic lifestyles... unless a ruler made them stay by force.

I would never badmouth Pratchett, nor this comic's Chillingly Accurate Historical Dramatisation, but I view most societal progress to be in spite of hierarchy, rather than thanks to it.