HUMAN SETTLEMENT IN THE MIDDLE OGOOUE VALLEY
CLIMATIC SAVANNAS ISOLATED WITHIN THE FOREST
Following the long dry climatic phase of the Leopoldvillian, when savannas dominated the central African landscape, forests recovered in the humid Kibangian, reaching their present distribution around 6,000 B.P.(Maley 1987). Aubreville (1967) has already proposed that the “strange” middle Ogooue savannas (he termed them Booue) are a paleoclimatic relict. They have now been dated to around 9,000-8,000 B.P. using and analyses (Oslisly and White, in press; Oslisly et al. 1996), suggesting that they are a relict of the dry Leopoldvillian climatic phase, during which they would have been much more widespread. Further evidence that these are ancient savannas comes from the local presence of specialist savanna animals and plants: for example, such bird species such as the long-legged pipit, Anthus pallidiventris; the pectoral-patch cisticola, Cisticola brunnescens; and the black-faced canary, Serinus capistratus, which are thought unlikely to cross large expanses of forest (Christy and Clarke 1994; P. Christy, pers. comm.). Savanna frogs of the genus Ptychadena, considered good biological indicators of ancient grassland, are also present (Blanc 1998; C. Blank, pers. comm.), as is the bushbuck, Tragelaphus scriptus, a mammal that lives in savanna and woodland vegetation but which does not occur deep in the forest. The presence of these savanna specialists is good evidence that a savanna corridor once connected the middle Ogooue valley to Congo.
Identification of plant species from charcoal found in village sites known to have been located in the savanna demonstrates the presence of indicators of mature forest vegetation within the forest-savanna mosaic during the late Stone Age (White 1992, 1995). Further more, charcoal from the forest tree Pterocarpus soyauxii (Padouk) was favored by all Iron Age peoples for smelting ore and must have been obtained from within the forests of the period. This paints a picture of successive groups of peoples living in open savanna but making extensive use of nearby forests. It would have been their fires, lit to maintain their open habitat and, perhaps more important, to facilitate hunting of large savanna grazers, that prevented recolonization of the savannas by forest vegetation. Equally, during the hiatus when fires would, presumably, have been far less frequent, savanna areas were colonized rapidly by forest species, illustrating the important ecological role played by humans (Oslisly andWhite, in press).
Research from the middle Ogooue valley does not provide evidence of true forest dwelling until the quite recent past. Even sites discovered within the forest today were actually located within savanna vegetation when inhabited (White and Oslisly, unpublished data). This emphasizes the need to take into account vegetation history when considering the dynamics of central African peoples, as well as when attempting to interpret the significance of archaeological remains.
Because of the lack of sites in forested central Africa with well-maintained stratigraphy dating to early or middle Stone Ages, we are currently unable to say much about the way these earlier peoples lived. From about 10,000 B.P. onward we possess a relatively detailed picture of population dynamics in the middle Ogooue valley, which demonstrates the arrival of a long sequence of civilizations, particularly from the Neolithic (c. 4,500 B.P.) onward. It seems that the major migrations of Bantu ironworkers were linked to a dry climatic phase in the Kibangian B (3,500-2,000 B.P.), which probably resulted in decreased forest cover and may have enabled these savanna-dwelling peoples to avoid the prospect of a daunting trip into extensive forest vegetation (Maley 1992, Schwartz 1992;). These migrations were undertaken through Gabon following ridge lines (Oslisly 1995), although elsewhere river navigation was used (see, e.g., Eggert 1993). The migrating peoples seem to have favored areas with at least some savanna vegetation, reflecting their origins outside the forest ecosystem, and it is not surprising that the middle Ogooue valley was appealing to them. It seems that they systematically supplanted resident cultures, although it is possible that they also assimilated some local knowledge (see, e. g., Vansina 1990).
Elsewhere in forested Africa, as in the middle valley of the Ogooue, the recent Holocene was a time of successive waves of migrating Bantu peoples replacing resident populations. Hence, the overriding theme of human settlement in the middle Ogooue valley, as well as in other parts of Africa, is one of savanna dwelling peoples who made use of the forest environment but who preferred to avoid dwelling within it as true “forest peoples.” Therefore, this is not dissimilar to present patterns of migration within the forest zone, which tends to result in forest conversion. This study demonstrates the rich and dynamic prehistorical past of the middle valley of the Ogooue, particularly during the Holocene, a period for which there are numerous archaeological remains. lt also raises a number of questions, perhaps the most fundamental of which is: How important are these isolated savanna regions to the history of human populations in the middle valley of the Ogooue, and how has the long history of human habitation affected the savannas and the surrounding forest? Ongoing multidisciplinary research on archaeology, vegetation history, palynology, and plant ecology should provide answers and also reveal to what extent the history of human populations in the central African region as a whole mirrors that of the middle Ogooue valley.
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