The Holocene plant landscape of Gobero: palynology applied to palaeo-environmental and palaeo-ethnobotanical reconstructions

Gobero (600 m asl; 16°55’N – 9°30’E) is a paleolake surrounded by early-mid Holocene archaeological sites (1). It lies on the western edge of the Ténéré Desert, in central Niger, about 600 km NW of the Lake Chad. Approximately two hundred human burials on the edge of the paleolake provide a uniquely preserved record of human occupation in the Sahara under severe climatic fluctuation during the Holocene (2). The area of Gobero is presently in the hyperarid climate region of the southern Sahara (3). The permanent vegetation, including small shrubs and tufted grasses, is restricted to wadis and depressions where groundwater is close to the surface. Desert/sub-desert and ephemeric floras grow under scanty and variable precipitations (18 ±15.8 mm per year).The archaeological sites are situated in a closed depression with an endorheic drainage pattern. Some ephemeral streams, having small catchment areas extending immediately north and north-east of the sites, flow into the depression. During Holocene humid periods, a lake was formed inside the Gobero basin and, when the humidity was at its maximum, a spillway connected Gobero with the lake Chad. Based on stratigraphical-archaeological data and direct dating of human burials, two occupational phases are identified that correspond with two humid intervals, dating to the early and mid-Holocene, respectively. The older occupants, with a hunting-fishing-gathering subsistence basis, were buried in hyperflexed positions, and represent the most ancient known cemetery in the Sahara, between about 9700 and 8200 cal BP. The younger occupants adopted cattle herding and were of shorter stature with semi-flexed burials and grave goods including animal bones and ivory ornaments, between about 6900 and 4700 cal BP (1, 4). The site was also used as a habitation, as indicated by over 10,000 stone artefacts and over 4,000 ceramic fragments.In the framework of a large-scale multidisciplinary research, pollen data from the site of Gobero and its surroundings provided a primary contribution to reconstruct the past plant landscape of the region. The site also offers an incomparable set to study the evolution of a fragile and vulnerable environment, in which climate changes have played a crucial role for plants, animals and human’s survival. Samples were collected from the burial fillings and from desiccated lakebeds. Pollen spectra were obtained from 39 samples. They showed a low biodiversity. Ficus and Ziziphus-type were the most frequent pollen from woody plants, together with Capparis, Combretum-type, Myrtus and Salvadora persica. Spectra were herb-dominated (mainly Poaceae, Chenopodiaceae and Cyperaceae, together with Asteraceae and Plantago). Hygro-hydrophytes (Typha, Juncus, Nymphaea cf., Potamogeton) were common. The landscape was a mosaic of xeric and wet environments, covered by a grassland vegetation. The environment was wetter at the early Holocene than at the mid Holocene. In a few cases, pollen from burials has suggested that plants were collected to transport grasses, myrtle and capers as grave goods in the cemetery, possibly a thousand-years ancient behaviour of positioning plants near dead persons. 1) P. Sereno et al. (2008) PLoSONE 3(8), e2995, 1-222) National Geographic magazine, September 20083) F. White (1982), The vegetation of Africa, UNESCO 4) Garcea (ed.) in prep. Gobero: the No-Return Frontier Archaeology and Landscape at the Saharo-Sahelian Borderland. J. African Archaeology