Broad spectrum revolution

The Broad Spectrum Revolution (BSR) hypothesis, proposed by Kent Flannery in a 1968 paper presented to a London University symposium, suggested that the emergence of the Neolithic in southwest Asia was prefaced by increases in dietary breadth among foraging societies. The broad spectrum revolution followed the ice age around 15,000 BP in the Middle East and 12,000 BP in Europe. During this time, there was a transition from focusing on a few main food sources to gathering/hunting a "broad spectrum" of plants and animals.

Flannery's hypothesis was meant to help explain the adoption of agriculture. Unpersuaded by "the facile explanation of prehistoric environmental change", 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 deliberate cultivation of certain plant 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.

A BSR is likely to manifest as both an increased spectrum of food resources and an evenness in the exploitation of high- and low-value prey. Under a broad spectrum economy a greater amount of low-value prey (i.e. high cost-to-benefit ratio) would be included because there are insufficient high-value prey to reliably satisfy a population's needs. In terms of plants, it would be expected that foodstuffs that had once been ignored because of difficulty of extraction were now included in a diet. In terms of fauna, animal prey which was previously considered an inefficient use of resources (particularly small, fast mammals or fish) could now also be worthwhile. In other words, increasing scarcity made the extra effort necessary for survival.

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