5 Wild-Grass Seed Harvesting in the Sahara and Sub-Sahara of Africa JACK R
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5 Wild-grass seed harvesting in the Sahara and Sub-Sahara of Africa JACK R. HARLAN Introduction Over 60 species of grasses have been harvested for their grains in Africa. Most of these are famine or scarcity foods or are harvested casually and opportunistically. Several species, however, have provided food on a massive scale and have been staples for a number of tribes. These include: Aristida pungens, a staple of the northern Tuareg; Panicum turgidum, basic in central Sahara; Cenchrus biflorus, a major food of the Sahel; krebs, a complex of a dozen or more species including Panicum laetum, several species of Eragrostis, Dactyloctenium, Brachiaria, etc., providing staples from Bornu to Kordofan; Oryza barthii, widely harvested from swamps in the savanna, but a staple from Bornu to Kordofan; Paspalum scrobiculatum, a companion weed-crop of rice in the forest zone of West Africa; and Echinochloa stagnina, a sugar crop as well as a grain crop in the central Niger delta and around Lake Chad. Methods of harvest include: beating into a container, rubbing with the hands into a basket, cutting with a knife or sickle and threshing with a stick; using a swinging basket or calabash; sweeping or raking off the sand; tying up clumps with string before harvest. The grains are consumed in many forms: pounded and eaten raw; as dilute flour or semoula in a drink; gruel; porridge; flat bread; pastry; couscous; and beer. Bran may be removed in the mortar and used separately. Some of these practices may have started in the Palaeolithic, and they all have relevance to the processes of plant domestication and the beginnings of agriculture. Some of us who have studied plant domestication in Africa have noted that the continent appears to be a vast laboratory for the study of crop evolution (Harlan et al. 1976, p. 5). The progenitors of African crops are usually obvious, and the abundance of intermediate states and conditions makes the pathways of crop evolution easy to follow. This is not the case in the Americas, for example, where we have not identified with any assurance the progenitors of some domesticated Cucurbita and Capsicum species and where the origins of maize, sweet potato, tobacco, peanut, bottle gourd and the A genome of cotton are still under debate (cf. Heiser Ch. 30, Pickersgill Ch. 27, Wilkes Ch. 28, this volume). In Eurasia, we have yet to locate the B genome of wheat in a diploid species or the progenitors of fava bean, pigeon pea, the bottle gourd, and a few others (cf. Ladizinsky Ch. 23, Zohary Ch. 22, this volume). The story in Africa seems to be simpler and the evidence more clear-cut. Not only are intermediate states between wild and domesticated races still present, but ancient practices that may have had their origins in the Palaeolithic may persist into historical times when ethnographic observations could be recorded. A suite of these practices concerned with the harvesting of wild-grass grains for food is the focus of this chapter. Harvesting seeds from natural or induced stands does not necessarily result in domestication. The seeds of many species have been harvested for millennia without the evolution of domesticated races, but harvesting and developing some degree of dependence on a plant does establish the kind of intimate relationship between plants and people out of which plant domestication may proceed. Regularly scheduled harvests are probably a precondition for domestication, whether it takes place or not. The wild-grass harvests of Africa are, therefore, pertinent subjects for examination in the context of the evolution of plant exploitation in general and the emergence of cereal agriculture in particular. Grass-seed productivity. There seems to be a widespread misconception about wild-grain harvests to the effect that these are desperation or last-resort practices to avert starvation, and that yields are feeble and unpredictable. There are instances when this is so, but natural stands of wild grasses can give very respectable yields of high-quality food, and in some circumstances may be more dependable than cultivated crops. I have had some personal experience of these matters. For over 25 years, I directed research on seed production of several wild species, mostly native North American grasses. Yields of 500– 800 kg/ ha were not uncommon and 1 ton/ ha could occasionally be obtained. This is in the range obtained by many subsistence farmers growing domesticated cereals. Gallais (1984), for example, gives the typical yield of rice grown in the bend of the Niger as 6– 700 kg/ ha. Good yields with perennial species could not be sustained year after year even with fertilizers and irrigation; seed production of perennial grasses tends to be cyclic (Harlan et al. 1956). Annual species tend to yield more and be more dependable. The annual habit requires reseeding each year, and natural selection has favoured the partitioning of more metabolic effort into the reproduction phase of the life cycle than in perennial species, where annual reproduction is unnecessary. My often-cited experiment with wild einkorn wheat in Turkey yielded almost 1 kg of pure-grain equivalent per hour of work, and the grains were far more nutritious than domesticated wheat (Harlan 1967). Zohary (1969) performed a somewhat similar experiment with wild emmer in Israel and calculated the yield at 500– 800 kg/ ha. This is as much or more than farmers in England obtained from domesticated wheat in the Middle Ages (Titow 1972). Chevalier (1932) described an African wild-grass harvest (see below) and stated that one adult could easily gather 10 kg in a morning’s effort. There is no evidence that he actually weighed the harvest and the grains still had the hulls attached. Removal of the hull in Panicum would reduce the yield by about 20 per cent. But, making allowance for over-estimation and processing, the figure of 1– 2 kg/ h could surely be achieved and the effort would be highly rewarding. Indeed Evans (1975, p. 329) calculated that my wild wheat harvest returned 40– 50 kcal of energy for every kcal expended on my part, and this is far more efficient in terms of the ratio of consumable output energy to energy expended in harvesting than any form of agriculture so far studied. (However, see Cane Ch. 6 for a discussion of the high-energy costs of processing wild- grass seed once it is harvested.) On another occasion, I used a Mexican wooden paddle for a beater and a plastic wastebasket for a receiving container and harvested a stand of tall fescue (Festuca arundinacea Schreb.). Six 15-minute trials averaged a little over 1 kg per quarter hour or 4.5 kg/ h, if I worked hard and continuously. A real gatherer would probably work at a more leisurely pace, but it was necessary to fill the time interval with work in order to get a measurement. Decortication of the grain would reduce the yield of pure-grain equivalent by about 30 per cent, or in round figures 3 kg/ h net yield. I also conducted a harvest of teosinte or ‘wild’ maize (Zea mays ssp. mexicana (Schrader) litis) in Michoacan (unpublished). In five 30-minute trials, the average yield was 485 g cleaned, filled fruit-cases per hour. This is a much lower production in terms of grain equivalents than the others, but if one were to consume 150 g/ day, a short 3.5-hour gatherer’s day would accumulate more than a 10-day supply. This is still worth the effort, even though teosinte is not nearly as productive as many other grasses in terms of pure-grain yield. Hunter-gatherers have developed an appreciation for wild-grass grains the world over. They certainly would not overlook so rich a source of nutritious plant food, and especially one so easily harvested and stored for future use. Ethnographic data indicate that people have exploited this resource on a large scale on every continent, often harvesting different species of the same genera (Harlan 1975, pp. 15– 18). For Africa, Jardin (1967) lists about 60 species harvested in the wild. The exact number cannot be determined because of synonomy, and because few of the observers were botanists and reference specimens were seldom obtained. The number is conservative, and more species could be added. However, most of the species are, in fact, famine foods collected in times of scarcity or harvested casually as opportunity presents. I am not much concerned with these here, but concentrate instead on those harvested regularly on such a scale that they may be considered staples for some tribes. Wild- grass seeds are still harvested in Africa, but cultures have been so distorted and transformed in recent decades that a better picture of traditional diets and customs can be obtained from 19th- and early 20th- century observations than from contemporary studies. These suggest at least three distinct ecological zones of major wild-grain exploitation. The desert zone Aristida pungens Desf. Drinn (Arabic); tessiya (Tabelbala); tullult, touloult (Tuareg) This is a relatively tall (to 1.5 m) tufted perennial grass with a plume-like inflorescence and black grains when ripe which bear the triple awns characteristic of the genus. In this species all three branches of the awn are plumose. It grows in abundance in wadi beds and low areas that catch runoff from occasional rains. Duveyrier (1864) in his study of the northern Tuareg said it was the most common and widespread of the grasses and the most useful to the Tuareg, providing pasturage for their livestock and food for the people: ‘this grain is often the people’s only food’ (p.