“…First applied to the southern Transvaal (Wadley, 1987(Wadley, , 1989a, this model of seasonal aggregation/dispersal has since been taken up elsewhere, though in situations where data are neither as rich nor as varied (Barham, 1992;Wadley, 1992b;Mitchell, 1993a). Under conditions of social and/or ecological stress, exchange may be intensified (e.g., Wiessner, 1984, pp.…”