Lakeside cemeteries in the Sahara: 5000 years of holocene population and environmental change

Background: Approximately two hundred human burials were discovered on the edge of a paleolake in Niger that provide a uniquely preserved record of human occupation in the Sahara during the Holocene (∼8000 B.C.E. to the present). Called Gobero, this suite of closely spaced sites chronicles the rapid pace of biosocial change in the southern Sahara in response to severe climatic fluctuation. Methodology/Principal Findings: Two main occupational phases are identified that correspond with humid intervals in the early and mid-Holocene, based on 78 direct AMS radiocarbon dates on human remains, fauna and artifacts, as well as 9 OSL dates on paleodune sand. The older occupants have craniofacial dimensions that demonstrate similarities with mid-Holocene occupants of the southern Sahara and Late Pleistocene to early Holocene inhabitants of the Maghreb. Their hyperflexed burials compose the earliest cemetery in the Sahara dating to ∼7500 B.C.E. These early occupants abandon the area under arid conditions and, when humid conditions return ∼4600 B.C.E., are replaced by a more gracile people with elaborated grave goods including animal bone and ivory ornaments. Conclusions/Significance: The principal significance of Gobero lies in its extraordinary human, faunal, and archaeological record, from which we conclude the following: (1) The early Holocene occupants at Gobrero (7700-6200 B.C.E.) were largely sedentary hunter-fishers-gatherers with lakeside funerary sites that include the earliest recorded cemetery in the Sahara. (2) Principal components analasis of craniometric variables closely allies the early Holocene occupants at Gobrero with a skeletally robust, trans-Saharan assemblage of Late Pleistocene to mid-Holocene human populations from the Maghreb and suothern Sahara. (3) Gobero was abandoned during a period of severe aridification possibly as long as one millenium (6200-5200 B.C.E). (4) More gracile humans arrived in the mid-Holocene (5200-2500 B.C.E) employing a diversed subsistence economy based on clams, fish, and savanna vertebrates as well as some cattle husbandry. (5) Population replacement after a harsh arid hiatus is the most likely explanation for the occupational sequence at Gobrero. (6) We are just beginning to understand the anatomical and cultural diversity that existed within the Sahara during the Holocene.