Aspects of African Archaeology

The emergence of food production in the West African : new evidence from northeast and northern

KATHARINA NEUMANN, AZIZ BALLOUCHE AND MARLIES KLEE

Introduction

West , as we learned from Harlan and Harris twenty years ago, is [�tg�_Q�sJl1�.S:.flli!�JQ� tpem.ost important African seed crops. The maps published by Harlan (1971) and Harris (1976) show the hypothetic domestication areas of the staple crops Pennisetum americanum, Sorghum bicolor and African rice (Oryza glaberrima) concentrating in a broad band stretching from the Atlantic Ocean to the Red Sea which at least partly coincides with the Sahel as defined by Le Houerou (1989). However, these maps were not based on archaeological plant remains, but exclu­ sively on the modern distribution of the hypothetical wild ancestors of domesticated . As with the domestication history of cattle in North Africa (Gautier 1987), the dearth of direct archaeobotanical data coincides with a surfeit of models concerning the history of plant domestication. The few insufficiently documented grain impressions from Dhar Tichitt (Jacques-Felix 1971) - not pollen impressions, as erroneously interpreted by Andah (1993) - had to serve as the only evidence for a repeatedly cited model of the transition from foraging to farming (Munson 1976). Yet Amblard's long-term work in Dhar Tichitt (Amblard and Pemes 1989; Amblard, this volume) has shown that, even though the identifications of Jacques-Felix were right, the transition model based on his 525 identified casts can no more be regarded as valid. It is evident that more basic archaeobotanical data are needed before proceeding to the next step in formulating new models. This paper is a contribution to increase the data base. It refers to archaeobotanical research in the multidisciplinary frame of a Special Research Project at the Uni­ versity of Frankfurt/Germany, called "Culture, language and environment in the West African sa­ vanna". The sub-project "Vegetation history and archaeobotany" is in itself multidisciplinary as it is working with pollen, fruits and seeds and charred wood. Investigations concentrate on northern Burkina Faso and northeast Nigeria, both lying on the southern edge of the Sahel (Fig. 1).

The plant remains from Kursakata, northeast Nigeria

In northeast Nigeria, charred plant remains have been found in various settlement mounds of the Chad basin. The site of Kursakata (Fig. 1), situated at the edge of the firki clay plains, was exca­ vated by Graham Connah in 1965 (Connah 1981) and revisited by the Frankfurt team in 1994 442 Katharina Neumann et at.

Figure 1 Sites mentioned in the text.

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(Gronenbom, this vo1.). It yielded well-preserved fruits and grains down to a depth of five metres. Among more than 40 different taxa, by far the most important group is that of the grasses, consist­ ing of small-grained Paniceae, Pennisetum and rice COryza). Paniceae are a large tribe of the grass family with a centre of distribution in the Sahel, including such well-known species as Digitaria exilis, Panicum laetum, Cenchrus biflorus and Paspalum scrobiculatum (Harlan 1989). Even today, grains of many Paniceae species are collected on a large scale for food, often called kreb or fonio, and are sometimes sold in the markets. Collecting is done either by beating the grains into a basket or sweeping them from the ground after they have fallen from the plant at maturity. With the excep­ tion of Brachiaria deflexa, small-grained Paniceae are usually not cultivated and we interpret their appearance in archaeological deposits as an indicator of collecting activities. The second important grass from Kursakata is rice (Oryza). Today, two species of wild rice COryza barthii and o. longistaminata) are widely distributed on the clay soils of the Lake Chad area. Collecting of wild rice is commonly practised by breaking bundles of the upper parts of the panicles into a basket. At the moment we are not able to determine if the rice from Kursakata can be attributed to one of the two wild species or to domesticated African rice, Oryza glaberrima. From the ethnobotanical evidence we suggest that the rice of Kursakata probably also belongs to one of the wild species. The third grass is Pennisetum americanum, bulrush millet, today one of the world's most im­ portant crops. To understand the significance of Pennisetum in the archaeobotanical material, we refer to the differencesbetween wild and domesticated millet as published by Brunken et al. (1977) and Amblard and Pemes (1989). In the wild and weedy forms the spikelets break off at maturity, leaving the naked axis whereas in domesticated Pennisetum the pedicelled spikelets containing the grains stay connected with the centralaxis at maturity, such making harvesting of the whole inflo­ rescence possible. Unfortunately the material from Kursakata does not contain the characteristic The emergence of plant food production in the West African Sahel 443

Figure 2 Pennisetum americanum, comparison between modern wild (left), modern domesticated (middle) and charred grains from Kursakata (right). Pennisetum americanum (L.) LEEKE

modern Kursakata (depth: 320 cm) subsp. monodii subsp. americanum (wild) (domesticated)

1mm I

spikelets, but only the naked grains, and so identification has to rely to grain morphology (Brunken et al. 1977). Grains of modern wild Pennisetum are elliptic and less then 1 mm deep, while domes­ ticates are club-shaped and much deeper and wider in the upper part. In the material from Kursakata, there are charred grains of Pennisetum which are clearly club-shaped even though they are gener­ ally smaller than the recent domesticated forms (Fig. 2). However, as shape is a more reliable char­ acter than size for distinguishing wild and domesticated millet, we conclude that our Pennisetum grains, at least partially, belong to a domesticated type. The beginning of the archaeobotanical sequence at Kursakata is dated to 2860 BP (Fig. 3). The Pennisetum curve starts at about 4,40 m - grains found at this depth are clearly domesticated - and rises sharply at about 4 m. Rice and Paniceae are present throughout the profile. These results are only preliminary and we do not want to interpret them quantitatively. However, we can say the .people of Kursakata had domesticated Pennisetunz shortly after 2800 BP, and at the same time, �ollecting of �li(t2!ant�_�!illpiayed -an important roie�-Thi-s mTxecfeco-nomywith Pennisetum culti­ vation and col�£!!!!Kof wiler-grasses-continuecf16r-about 1000 years. In the uppermost 140 cm, Pennisetum is no more present Whereas-ihecurvesofPanIc-e-ae-anclflcecontinue. However, as only a small part of the site has been excavated, conclusions about a changing economy after 1900 BP cannot be drawn at the moment. Collecting activities in Kursakata are furthermore indicated by the presence of wild fruit spe­ cies, such as Ziziphus sp. , Celtis integrifolia and Vitex cf. doniana. The first two taxa are part of the modern natural vegetation in the Chad basin whereas Vitex doniana is a tree from more southern areas with higher precipitation (Aubreville 1950). At the moment we are not able to decide whether the species was growing in the vicinity of the site with a better water supply than today or the fruits were imported from the south. 444 Katharina Neumann et al. OOS +1 06" -.occo a.. E aS" coo ::::s N..o Q) � OL" ctS Q) Q) en 09" ctS .2 N c as" c c ctS � Q) 0"" a.. o a.. O£" II n OZ" u 01" +1 00" o a.. 10CC 06£- NO NCO OS£ OLE 09£ OS£ . ..- ...... " ...... '.:« .;-:.' 0,.£ O££ OZ£ ,'«<-:-:-:-:<.:-:-' 01£ ... «<-:< ...... ,-:-:- 00£ E 06Z u OSZ c OLZ .c � 09Z Q.. OSZ Q) 0 O,.Z O£Z OZZ OlZ OOZ 061 OSl OLl 091 OSl +1 0,.1 o a.. NCC �rrr-c- 0-.0 OZl t-I.t') 011 001 06 OS OL 09 os 0,.

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Figure 4 Oursi (Burkina Faso), simplified pollen diagram with the main elements.

Oem

em 60 610 ± 40 BP

B,

3130 ± 80 BP

A

7720 ± 80 BP 446 Katharina Neumann et al.

The pollen profile of Oursi, northern Burkina Faso

With the data from Kursakata it can be shown that agriculture based on Pennisetum was practised shortly after 2800 BP in the Lake Chad area. This must have exerted a profound impact on the vegetation which might be seen best in a pollen diagram. Unfortunately the sediments of the Chad basin are not suitable for pollen analysis. To demonstrate the vegetation change brought about by agriculture in a Sahelian environment, we have to move from NE Nigeria to northern Burkina Faso, the other working area of the University of Frankfurt project (Fig. 1). From the temporary lake of Oursi in the province of Oudalan, a pollen profile has been obtained covering the complete Middle and Late Holocene (Ballouche and Neumann 1995). In this paper, we are presenting a simplified version of this diagram with only the most important elements (Fig. 4).

In zone A (275 cm - 175 cm), the high percentages of grasses and the low values of tree pollen (some acacias and a few ) lead us to assume that the local and regional vegetation was a closed grassland with only very few woody plants. For this period, no traces of human impact on the vegetation can be detected. At a depth of 175 cm with two radiocarbon dates around 3000 BP, a marked change is visible in the diagram. In zone B (175 cm - 0 cm), the percentages of grasses decrease, and at the same time three groups of taxa increase: the tropical woody family Combretaceae, a group of several herbal taxa and Mitracarpus. This development even intensifies after 600 BP (zone B2). Cyperaceae are indicators of the local vegetation, most probably a belt of reeds which was expanding when the lake became more shallow. We think that the increasing percentages of the other three taxa are pointing to the changes brought about by agriculture. In the region of Oursi, clearing for fields did not take place in a forest area as in temperate or humid tropical zones, but in a closed grassland. This natural grassland is represented in zone A of the diagram. Clearing resulted in an opening of the grass cover, finding its expression in decreasing percentages of grasses in zone B of the diagram. In addition, the increasing percentages of herbs are most probably representing the weedy flora of the fields. The most important weed is Mitracarpus villosus, a plant which is missing in modern "natural" Sahel ian grasslands, but which is widely distributed in fields, very young fallows and other habitats disturbed by man (Neumann and Ballouche 1995). Combretaceae are a large tropical plant family with exclusively woody species. We think that most of the Combretaceae pollen in the Oursi diagram comes from a species called glutinosum which is a dominant constituent of the modern vegetation on the dunes of Oursi. Combretum glutinosum today is one of the most common plants of the southern Sahel and it plays an important role in the system of shifting cultivation. The cultivation cycle of Pennisetum starts with a complete removal of grasses and herbs and cutting of trees and shrubs at the height of a few centimetres above the ground. After some years of cultivation the soils will be exhausted and the fields are left for fallow. Only a few woody species which are able to produce suckers can regener­ ate on the former fields, and Combretum glutinosum is one of them. If no further clearing takes place, the plants can grow up to the height of small trees and in the course of 10 to 30 years a typical Sahelian savanna will develop. These Sahelian savannas with dominating Combretum glutinosum are not natural, but they can be regarded as a large area of fallows, such representing an advanced stade of degradation of the original plant communities (Trochain 1940: 171). Thus we have drawn the conclusion that the rising curve of Combretaceae in zone B of the diagram represents an agricul­ tural system with fallows the origins of which can be traced back to 3000 BP.

Conclusion

As a conclusion we can state that there is evidence for an almost synchronous beginning of agricul­ ture after 3000 BP in the Chad basin and in the dune areas of northern Burkina Faso. In Kursakata, macro-remains of domesticated Pennisetum indicate that this crop was grown on the sandy islands The emergence of plant food production in the West African Sahel 447

of the firkiplains. At the same time, collecting of wild grasses continued to play an important role in the economy. In the pollen profile of Oursi the decreasing percentages of grasses and the increasing percentages of several herbs, Mitracarpus and Combretaceae represent an agricultural system with fields and fallows. The pollen diagram of Oursi shows that the beginning of agriculture in the Sahel had a marked effect on the vegetation which might have masked the effects of a possible climatic change.

Acknowledgements

We wish to thank the German Research Foundation for funding the Project "Culture, language and environment in the West African savanna". We are indebted to Stefanie Kahlheber for the drawing of Pennisetum and to Barbara Zach, Monika Heckner and Ulrich Salzmann for their help with the diagrams.

References

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