This theory assumes that developing that sort of society is a step that every group will take if given the opportunity.
I would think it's entirely possible for a group of people who could switch to systematic agricultural life not to do so, for several different reasons. They might just not think of doing it. They might predict that it would make things worse rather than better (and I've seen it suggested that the transition from hunting-and-gathering to agriculture really did make things worse rather than better for quite some time, even though it eventually enabled the rise of modern society with all its advantages). They might not want to take the risk. They might see the hunter-gatherer lifestyle as favoured by gods or ancestral spirits or what-have-you and think they shouldn't change.
If that's right, then you can't infer anything much from the fact that a given group of people didn't switch from hunting-and-gathering to something more settled and complicated.
You don't need a whole group to choose to switch to agriculture; just one innovator to show that it works better and the others to not burn that person at the stake for doing it. I say agriculture; but it could be as simple as. I try to encourage this plant to grow more by spreading its seeds, Oh look we have lots of food-plant-X now. Or:
My point (which I am really not showing well) is that the early stages...
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