The broad spectrum revolution (BSR) hypothesis, proposed by Kent Flannery in a 1968 paper presented to a London University symposium,[1] 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 most recent 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.