 Approximately 10,000 years ago, desertification forced hunter-gatherer societies south into the Sahel regions of northern Central Africa, where some groups settled and began farming as part of the Neolithic Revolution.Initial farming of white yam progressed into millet and sorghum, and then later the domestication of African oil palm improved the groups' nutrition and allowed for expansion of the local populations.Bananas arrived in the region and added an important source of carbohydrates to the diet; they were also used in the production of alcohol.