THE ROCK ART OF WESTERN CENTRAL AFRICA

	HUMAN SETTLEMENT IN THE MIDDLE OGOOUE VALLEY	Page 9/10

A new wave of ironworkers arrived in the middle Ogooue valley around 1,900 - 1,800 B.P. and took up residence on the hilltops vacated by the Okanda peoples. Apparently, after inhabiting the area for four or five centuries, they moved away to the south, following ridges through the forest to the savannas that descend toward the center of the Massif du Chaillu to the west of the Offoue river, and then on to the savannas of the upper Ogooue and northwest Congo. Such a scenario corresponds well with the more recent radiocarbon dates of iron smelting at Moanda in the upper Ogooue valley around 2,300 -1,800 B.P. (Digombe et al 1988) and on the Bateke plateau around 1,600-1,500 B.P. (Pincon et al. 1995). The Otoumbi ironworkers used the same smelting methods as the Okanda, but their pottery styles were new, with medium-sized pots that had out-curving lips and flat bases, decorated with indented lines, as well as small bowls with incurving lips. They were without handles and the decoration was more complex. A new style applied with a notched wheel appeared, and concentric circles were no longer featured. Similar pottery has been found 200 km further north in Gabon, at the Oyem 2 site in refuse pits dated to 2,300-2,200 B.P. (Clist 1989), and although data are few, the indications are that the Otoumbi ironworkers arrived in the savannas of the middle Ogooue valley from the forests to the north. These peoples expanded out from the Otoumbi area (see figure 7.5) between 1,900 and 1,600 B.P. along either side of the river and along ridgelines into the forest to the south, leaving tell-tale furnaces (at Anzem 1 and Mingoue 5) as well as large areas of charcoal from forest fires, dated to 1,500 - 1,400 B.P. (Oslisly and Dechainps 1994). These charcoal deposits represent the first evidence in the region of people with an itinerant slash-and-burn lifestyle living within the forest. Whereas the presence of ironworkers in the region has been confirmed for the period 2,500 - 1,500 B.P., radiocarbon dates suggest that between 1,400 and 800 B.P. the middle Ogooue valley was devoid of humans. No remains from this period have been found among seventy five sites dated so far (Oslisly 1993a, 1995). This suggests that a brutal phenomenon affected Iron Age peoples such that the region was empty until the arrival of the peoples of the recent Iron Age, who were the ancestors of populations present in the area today. The effect is not due to an ananomaly in the calibration curve of 14C values with time, because it is essentially linear during the period in question (Stuiver and Becker 1993), and indeed the phenomenon is not restricted to the middle Ogooue valley; human remains dated during this period are rare throughout Gabon. The carbon dates that do fall between 1,400 and 800 B.P. are spread across the three coastal provinces, Nyanga, and the Haut Ogooue, but there is no evidence of human populations during the same period in the four other provinces of Gabon, which account for 46% of all carbon dates available for the time period (90 of a total of 194).

Distribution of uncalibrated radiocarbon dates between 2,500 and 100 B.P. Adapted from Oslisly 1998.

Was this hiatus caused by a severe epidemic? The tropics are certainly recognized as a region of crippling endemic diseases where sudden outbreaks can devastate human populations. For instance, early in the twentieth century bubonic plague devastated populations in many parts of Gabon (Deschamps 1962). At the start of my work, I was surprised to find sites that seemed almost intact, with artifacts lying on the surface of the ground as if suddenly abandoned. In an area where conditions were already difficult and settlements small, a serious illness could have decimated Iron Age communities in a very short time. This seems to be the most likely explanation for the population void and may even be the reason for the current low human population density. It would not be surprising if such an epidemic led to a taboo, preventing repopulation of the area by surrounding peoples. The six-hundred-year “human silence” most likely led to significant changes in the forest-savanna mosaic of the middle Ogooue valley. Anthropogenic fires, which currently maintain the savanna, would have been much less frequent, and the forest would have expanded dramatically, given that humid conditions favorable for forest growth have been prevalent in the region since 2,000 B.P. Ironworking populations reappeared in the middle Ogooue valley from 800 B.P. and again occupied hilltop dwelling sites. Ceramics of this period include large and small pots of flattened spherical shape with out-curved apexes and pots of uneven curvature, as well as clay pipes. The decoration of these pots is unique, with small circular motifs made with knotted strips of plant material arranged in herring-bone patterns. The designs on pots form a band of variable width high on the sphere, and similar patterns are found on the clay bowls of pipes. This distinctive pattern has also been found on a pot from a cave at Lastoursville, 150 km upstream (Oslisly 1993a, 1995). Seeds of Sesamum cf. calycinium (Pedaliaceae - a species of sesame), which, when pounded, yield edibl oil, were found on the inside of this pot. Carbon dates from sites containing this style of pottery confirm historical and linguistic studies of the Okande peoples currently resident in the area (Ambouroue-Avaro 1981), which suggest that their ancestors arrived in the region around the fourteenth and fifteenth centuries. This same style of pottery, named Lope, has been found in an area greater than 1,500 km.sq. in size and indicates that a unified cultural group occupied at least 250 km along the length of the Ogooue valley. This would have been possible because of these people’s renowned skill at navigating the rapids of the Ogooue by dugout canoe, described by Savorgnan de Brazza in 1876 (Brunschwig 1966). New and ongoing research has revealed numerous furnaces and extensive remains of slag along ridgelines opened up by logging roads in the middle valley of the Leledi to the south of the Ogooue in a forested area at about 500 m altitude. Carbon dates fall between 800 and 200 B.P. Associated pottery found to date has been badly weathered, but the form, pattern, and composition are completely different from those of the Lope tradition. Iron-smelting furnaces of these peoples consisted of holes dug to about a meter down into the sandy-clayey layer, into which alternate layers of iron ore and charcoal were loaded, with large clay pipes angled downward, through which air was pumped by means of a bellows into the base. Previous smelting technology used in the middle Ogooue valley had involved the erection of a clay structure above ground, which had to be broken open and destroyed to obtain the iron. This new method would have facilitated removal of metal and waste and subsequent reloading and reuse (Collomb 1977), distinguishing between these recent Iron Age peoples and those of the early period. Hence, from the fourteenth through the nineteenth centuries, ironworkers in the region lived both in savanna (Lope peoples) and within the forest (Leledi tradition), extracting iron using the same technology but making pottery with different form and decoration. We will have to undertake further research to ascertain whether there was any commercial or cultural exchange between these two groups. It is a sad reflection on “progress” that pottery traditions which had lasted about 4,500 years rapidly became extinct with the massive recent importation of containers from Europe. Pottery is no longer made or used in the middle valley of the Ogooue. → Africa Rock Art Archive
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