Broad spectrum revolution

The Broad Spectrum Revolution (BSR) hypothesis, proposed by Kent Flannery in a 1968 paper presented to a London University symposium, [Kent Flannery, "Origins and Ecological Effects of Early Domestication in Iran and the Near East," "The Domestication and Exploitation of Plants and Animals", eds. Peter J. Ucko and G.W. Dimbleby (Chicago: Aldine Publishing Co., 1969), 73-100] suggested that the emergence of the Neolithic in southwest Asia was prefaced by increases in dietary breadth among foraging societies.

Flannery's hypothesis was meant to help explain the adoption of agriculture. Unpersuaded by "the facile explanation of prehistoric environmental change," [Flannery, 75] he suggested (following Lewis Binford's equilibrium model) that population growth in optimal habitats led to demographic pressure within nearby marginal habitats as daughter groups migrated. The search for more food within these marginal habitats forced foragers to diversify the types of food sources harvested, broadening the subsistence base outward to include more fish, small game, water fowl, invertebrates likes snails and shellfish, as well as previously ignored or marginal plant sources. Most importantly, Flannery argues that the need for more food in these marginal environments led to the delibrate cultivation of certain plants species, especially cereals. In optimal habitats, these plants naturally grew in relatively dense stands, but required human intervention in order to be efficiently harvested in marginal zones. Thus, the broad spectrum revolution set the stage for domestication and rise of permanent agricultural settlement.

The broad spectrum revolution has been a subject of intense debate since it was first proposed, but its basic arguments have borne up well. [see, for example, Mary Stiner, "Thirty Years on the 'Broad Spectrum Revolution' and Paleolithic Demography," "PNAS", 98, no. 13 (2001): 6993-6996; and Ehud Weiss "et al.", "The Broad Spectrum Revisited: Evidence from Plant Remains," "PNAS", 101, no. 26 (2004): 9551-9555]