Levi-Strauss, observing the Nambikwara, notes that they live in "what were effectively two very different societies" (Graber / Wengrow's summation)
"they were effectively moving back and forth, each year, between what evolutionary anthropologists [...] insist on thinking of as totally different stages of social development: from hunters and foragers to farmers and back again"
111: "You can't speak of an evolution from band to tribe to chiefdom to state if your starting points are groups that move fluidly between them as a matter of habit"
"seasonal dualism"
see also Marcel Mauss' "double morphology," in which a tribal group could have two entirely different social structures at different times of year
Mauss / Beuchat (1903), "Seasonal Variations of the Eskimo"
the circumpolar Inuit "and likewise many other societies ... have two social structures, one in summer and one in winter, and that in parallel they have two systems of law and religion"