More than 40 years ago Kent Flannery coined the term Broad Spectrum Revolution (BSR) in reference to a broadening of the subsistence base of Late Pleistocene hunter–gatherers in the Near East that preceded and helped pave the way for the domestication and plants and animals and the emergence of agriculture. Set within a demographic density model that projected differential rates of population growth and emigration in different resource zones of the Near East, Flannery’s BSR quickly became a global construct linking resource diversification and intensification to imbalances between population and environmental carrying capacity. In recent years the BSR has proven especially attractive to researchers working within an optimal foraging theory (OFT) framework in which diversification and intensification of subsistence only occurs within the context of resource depression, caused by either demographic pressure or environmental deterioration. This OFT perspective, that situates human societies in a one-way adaptive framework as they are forced to adapt to declining availability of optimal resources, however, is increasingly being called into question. Numerous examples of diversification and intensification are being documented in contexts of resource abundance shaped, in part, by deliberate human efforts at ecosystem engineering intended to promote resource productivity. An alternative approach, framed within a newer paradigm from evolutionary biology, niche construction theory (NCT), provides a more powerful explanatory framework for the BSR wherever it occurred.
