Research Shows Sahara's Green Past

From 5,000 to 11,000 years ago, what is now the Sahara Desert had 10X the rainfall it does today and was home to hunter-gatherers who lived in the region's savannahs and wooded grasslands. By analyzing marine sediments, rainfall patterns in the Sahara during that 'Green Sahara' period have been pinpointed. The work is more incremental than discovery, the existence of the Green Sahara period was already well-known, but this is a continuous record of the region's rainfall going 25,000 years into the past and it bolsters archaeological evidence which found that humans occupied much of the Sahara during the wet period, but left for about a thousand years around 8,000 years ago. This continuous rainfall record shows a thousand-year period about 8,000 years ago when the Sahara became drier, which coincides with when people left. "What's interesting is the people who came back after the dry period were different--most raised cattle. That dry period separates two different cultures. Our record provides a climate context for this change in occupation and lifestyle in the western Sahara," says lead author Jessica Tierney of the University of Arizona.