Author: Winshall, Robert,
Title: "When the Sahara Turned from Green to Brown--Postglacial Climate Change and Human Settlement in Central Sahara, 12,000 - 2,500 BC."Date: 1996 Institution: California State University Advisor: Alan Almquist Degree: M.A.
Abstract: For decades, archeologists have been aware of evidence suggesting that the Sahara Desert was much wetter and greener thousands of years ago. It is now possible to characterize these locations, in terms of both aquatic and terrestrial biota, but by also providing some data on the human inhabitants of these ecotomes. This thesis focused primarily on the features of human settlement in the central Sahara, looking at lifestyles of the people and examining factors favoring a wetlands economy. Finally, as the once-favorable conditions began disappearing, analysis of the destiny of these Saharan peoples is made.
The Holocene followed the last glacial age, about 12,000 BC. The temperatures in the Sahara became appreciably warmer and the climate demonstrated a lower evapotranspiration rate. The Intertropical Convergence Zone (ITCZ), the line along which north and south weather fronts converge, seems to have moved several hundred miles to the north. Since, in general, African rainfall north of the equator increases as one heads south, the shift of the ICTZ resulted in Saharan and sahelian zones receiving increased rainfall.
In addition to more temperate plant and animal species moving into the Sahara, the increased moisture resulted in lakes and rivers filling far beyond their prior capacity. In some cases, rivers breached their normal watershed, connecting with other systems. This allowed a broader distribution of aquatic species. In some areas, there were widespread wetlands. The earliest such sites, when associated with human habitation, date from ~7000 BC (with harpoons) and 6000 BC (wavy-line pottery). Because they used pottery, these cultures were originally considered some kind of Aquatic Neolithic.
JEG Sutton, in a 1974 article, called them the "Aquatic Civilization of Middle Africa". Although they did little stonework, he saw their bone work as very sophisticated. He suspected that much of their material culture, made of perishable materials, would not have survived. He thought them "victims" of stone-oriented scholars. Based on geographic distribution. he thought that the ancestors of Saharan, Songhai and Chari-Nile-speakers were these same "Middle Africans".
After the initial Holocene (postglacial) wet phase (12,000-7000 BC), conditions became drier for 500-1000 years. This was fol- lowed by a lesser wet phase of 2000 years. From then until 2500 BC, there was a gradual increase in dryness. After that time, weather conditions have been largely unchanged until the present. How did the human economies change with the climate?
The early harpoon-fishers availed themselves of large riverine and lake species, such as the Nile perch (known to exceed six feet). Whether they were fully-settled or did some amount of yearly travel isn't known. Undoubtedly, as water-tables dropped, the people needed to augment their aquatic diet with other foods. Initially, these would be available plant and animal foods which could be gathered.
Christopher Ehret's work touched on Sutton's language hypothesis--that these early fishers were NiloSaharan speakers. In the process of generating protolanguages for these speakers, he created an initial vocabulary for both NiloSaharan, proto-Saharan and proto-Sahelian. The words that he developed do not include fish or fishing terms (line, net, hook, harpoon). This early vocabulary does have herding terms and words for 'goat', 'young goat', 'cow', 'corral' and such. No other writers dealt with this topic.
The Central Sahara is punctuated by large stone outcrops--massifs--that create their own microclimate. In some cases, they represent a refuge for rare species, extinct everywhere else. Work by Henri Lhote in the 1950's documented the varied and colorful rockpaintings found in the massifs. Grouped into 23 styles, they are grouped as 1. Bubalus (extinct buffalo) hunters, early Neo- lithic; 2. 'Bovidian' pastoralists (considered Neolithic); 3. Equine phase, involving pastoralists with chariots and cavalry; 4. Phase of the camel, 1 AD. These groupings are disputed, but the images show us a wild-animal phase, then so-called 'Roundhead' figures. These appear to be multi-ethnic, including a 'Negroid' population.
The pastoralist period involved humpless cattle with large curved horns, similar to the ancient Egyptian Longhorn. Features of the people's life resemble activities of the Peul/Fulani, a contemporary West African pastoral group. Some of the boat images re- semble those on Egyptian monuments, raising yet other possibilities. Pastoralism appeared about the time that weather condi- tions became considerably drier (7000 BC), suggesting that it was a selected response to changing conditions.
The equine phase and its suspected timing may represent the arrival of the "Peoples of the Sea", groups that left Crete about 1500 BC (around the time of the Trojan War) and migrated northeast, east and southeast. The Biblical Philistines are one such group. Cretans arrived in NE Africa about 1200 BC, joining with the Libyans and attacking Egypt. Similar groups may have moved in from the coast and entered the central Sahara via the caravan trails. If so, this movement is more a political one than a response to climate change in the central Sahara, although its outcome would affect the local population.
Although the rock art isn't datable, it nevertheless shows us several different worlds of the central Sahara. The earliest involves Africa's megafauna (lions, elephants, etc) and Negroid peoples. Another one shows herding people with cattle. Some features of these images recall West Africa, others, Egypt. The herders look more like Somali people, with narrow noses, thin lips, straight hair. Probable intruders with horses and chariots are seen and, finally, the camel makes its appearance. Are the earlier people migrants from North Africa, from Egypt or from elsewhere?
Dhar Tichitt in southern Mauritania has been instructive as showing the cultural response to a drier climate. Digging revealed eight phases, from hunting megafauna (2000 BC), to limited hunting, gathering and herding (1500-1100). Subsequent phases included significant milling. The involved plant went from cramcram, a spiny famine food, to millet and sorghum. Identification of the species showed that the people had switched from gathering wild grasses to planting them, in about 100 years. Such speed is unheard of under normal circumstances, and suggests that the people were somehow "presensitized" to cultivation, perhaps via a smaller outgroup that grew up with farming and then migrated here. Both herding and planting were presumably responses to unfavorable climate. The site was abandoned after horses and metal weapons arrived, possibly with the charioteers described above.
The future of the central Saharans was not always the same as at Dhar Tichitt. Evidence suggests that the people migrated, some southwest, some southeast, some perhaps north, following the drying riverbeds as they sought sites where they could sus- tain themselves. Since West Africa had not yet been favorable to settlement, due to its dense forests, the central Saharans may represent some of the early ancestors of some of these peoples.