They think literally everyone was a hunter gatherer, there was no communities that weren't family units and every one of those family units that never interacted ever with anyone else unless doing warfare ALL got the Agriculture Perk when Humans got enough Evolution EXP by eating mammoths and all individually started small yeoman farms. Then some strong guy got other strong guys and called himself a king and united all these individual yeoman farmers against their will and made them share so he could something something cause that's their current stupid paranoia and they don't understand how culturally malleable people are. We may be genetically the same as the frozen cave dwellers we dig up but if you went back to even the time of your great grandparents you'd find yourself in a totally foreign and to you probably hostile place.