The Origins of African Metallurgies
- Augustin F. C. HollAugustin F. C. HollXiamen University
Sustained archaeological research has been conducted in different parts of the continent from the early 1980s on. Evidence of copper and iron metallurgies is documented in the continent, in West, Central, and East Africa. Early copper metallurgies were recorded in the Akjoujt region of Mauritania and the Eghazzer basin in Niger. Surprisingly early iron smelting installations were found in the Eghazzer basin (Niger), the Middle Senegal Valley (Senegal), the Mouhoun Bend (Burkina Faso), the Nsukka region and Taruga (Nigeria), the Great Lakes region in East Africa, the Djohong (Cameroons), and the Ndio (Central African Republic) areas. It is, however, the discoveries from the northern margins of the Equatorial rainforest, North-Central Africa, in the northeastern part of the Adamawa Plateau that radically falsify the “iron technology diffusion” hypothesis. Iron production activities are shown to have taken place as early as 3000–2500bce in habitation sites like Balimbé, Bétumé, and Bouboun, smelting sites like Gbabiri, and forge sites like Ôboui and Gbatoro. The last two sites provide high-resolution data on the spatial patterning of blacksmiths’ workshops dating from 2500 to 2000bce. Challenging data such as these are usually ignored or dismissed without serious consideration, but patient and sustained long-term research is contributing to a new understanding of the development of copper and iron metallurgies in Africa, enriching the long-term history of technologies.
Metallurgy: One or Many Inventions?
The advent of copper and iron metallurgy is one of the most fascinating debates taking place in African archaeology. This debate, with multiple implications, has a long history. It is anchored on 19th-century evolutionism and touches on the patterns and pace of technological evolution worldwide. It has also impacted the history of discourses on human progress. As such, it has strong sociopolitical implications. It was used to support the assumption of “African backwardness,” an assumption according to which all important material and institutional inventions and innovations took place elsewhere—in the Near East precisely—and spread from there to Africa through demic and stimulus diffusion. Does such a scheme capture global human technological history or is it a specific case of local areal development? That is the core of the ongoing debate on the origins of African metallurgy.
The Utilitarian Principle
Read from the utilitarian principle perspective, human history is but a long-term search for a better technological fit through the invention of increasingly efficient tools. Accordingly, technological systems tend to be considered as “self-driven autonomous” entities. But technology is not an entity in itself; it is a field of interaction (Adams 1996, 277). The evaluation of technological innovations’ impacts on African Late Holocene societies is usually based on an intuitive assessment of the efficiency of new materials and tools. They are supposed to have enhanced the harnessing of a greater amount of energy, streamlined production processes, increased productivity, generated important economies of scales, etc. It is generally asserted that iron-working was a technical innovation with quasi-revolutionary consequences:
In the Southern half of Africa, the story is completely different. Here the coming of iron was a catalyst which woke up half of a continent from the slumber of the Stone Age. The food-producing revolution of the Near East, which set the stage for the ensuing Bronze Age, had penetrated only as far as North Africa, the Nile Valley, and the Red Sea coast.(Van der Merwe 1980, 464)
Agricultural tools generally remained primitive in the early civilizations. The Inkas, Aztecs, and Shang Chinese relied on wooden digging sticks equipped with foot-bars to turn the soil, while their cutting tools were made of stone. The Mesopotamians and Egyptians employed light, ox-drawn plows to conserve soil moisture and prepare the soil for planting; Mesopotamian plows were also equipped with drills to plant seed. While Mesopotamians began to use copper hoes and sickles during the Early Dynastic Period, as late as the Middle Kingdom the Egyptians continued to edge their cutting tools with chipped flint.(Trigger 1993, 33)
In summary, despite its prevalence and commonsensical appeal, the utilitarian principle does not hold in the case of the initial use of metal artifacts. The scarce and precious metals were turned into status objects—weapons, items of personal adornment, symbols of power—used to display ascribed and achieved social positions. It is only later, after a few centuries and very likely more, when the technologies were mastered and widespread that production trickled down to the manufacture of tools used in productive activities.
The Origins of African Metallurgies
The first salvo of the debate on the origins of African metallurgies was fired in 1952 when R. Mauny published an essay on the history of metals in West Africa. H. Lhote reacted to that paper and suggested an alternative scenario. R. Mauny reconsidered Lhote’s objections and responded in the same journal in 1953. These two researchers (Lhote 1952; Mauny 1952, 1953) set the stage for what was to become a very interesting scientific debate (Bisson et al. 2000; de Barros 1990; Bocoum 2002; Haaland and Shinnie 1985; Holl 1997, 2004, 2009c; Killick et al. 1988; Killick 2001, 2004, 2016; Pringle 2009; Robertshaw 1990; Schmidt 1997; Tylecote 1975; Zangato and Holl 2010). Interestingly, there was hardly any appropriate set of archaeological data mobilized in the Lhote–Mauny exchanges. The debate opposed two conceptions of the origins of African metallurgies: the “single” and the “multiple” origins hypotheses. Mauny (1952, 1953) advocated the former scenario and Lhote (1952) the latter.
The Single Origins Hypotheses
The single origins hypotheses are based on the conviction of the uniqueness of the invention of iron metallurgy. It is claimed to have taken place in Western Asia, between Armenia and Anatolia in the early to mid 2nd millennium bce (Arkell et al. 1966; Huard, 1964; Van der Merwe 1980; Van Grunderbeek 1992, 72; Wertime 1973; Wertime and Muhly 1980). For Wertime (1973, 876), for example,
extractive-casting metallurgy was probably discovered in only one center, southwestern Asia, and . . .secondary centers developed over thousands of miles through the search for minerals. [In other words, once discovered and spread around in the initial core area] . . .iron migrated rapidly, reaching southeast Asia and China in the 7th century bce, Hallstatt Romania around 750 bce, and England between 500 and 400 bce. It never jumped to the Western Hemisphere; but in Africa, whose Bronze Age was spotty at best, it found its true prehistoric home, reaching Meroe in Nubia about 300 bce and coastal settlements of northwest Africa through the Phoenicians by 1000 to 1250bce. It spread quickly to Ghana but much more slowly to West and South Africa.(Wertime 1973, 885)
The possibility of parallel but independent invention was ruled out without further consideration for technical reasons spelled out in almost similar terms by Mauny (1967) and Phillipson (1985): “because the associated technology is so complex, and in earlier African societies no other process involved heating materials to such high temperature, we have to consider a northerly source of Sub-Saharan iron-working knowledge rather than duplicate independent discovery” (Phillipson 1985, 149). Wertime (1973, 885) emphasizes the same option: “only peoples with the very long metallurgical tradition possessed by the tribal peoples of Anatolia would have had the knowledge and patience to experiment with iron” (Grebenart 1985, 1988; Kense 1985; Van der Merwe 1980; Wertime 1973). Two diffusion itineraries were considered the most relevant: a northern one from Carthaginian North Africa and an eastern one from Meroe in Nubia.
The Meroe hypothesis was based on a visual impression. Large slag heaps were found in and around Meroe in the Nile Valley at the beginning of the 20th century. The locality was accordingly nicknamed the “Birmingham of Africa.” Located between the Armenian–Anatolian “cradle” of iron-working and the rest of Africa, Meroe was considered a key staging node of iron metallurgy. It was seasoned and acclimated to intertropical contexts, and from there, spread to the rest of the continent. This scenario was falsified by Trigger (1969) and Shinnie (1985) and shown to be incorrect.
The Carthaginian hypothesis was the only option left. Van der Merwe (1980) offers the most compelling formulation of the Carthaginian origins thesis:
They [Carthaginians] must obviously have had iron and the knowledge to produce steel, since their roots in the Eastern Mediterranean were practically in the heartland of iron-working of the time. No direct evidence for metal working has been found in Phoenician sites of the North African coast, but many references to iron and copper smelters occur on the stelae. Metal production probably took place elsewhere in the interior, the coastal towns having been sited for reasons other than a metal industry. Iron-working in this region is likely to have been of a utilitarian nature, with emphasis on the tools of war. The Phoenicians traded extensively with the Berbers, who in turn bartered with the Neolithic peoples south of the desert. To the existing trade of salt for West African gold and slaves the Berbers probably added Phoenician goods, including iron.(Van der Merwe 1980, 477)
Van der Merwe conflates material and events spanning a period of more than one thousand years. Aubet (2001) provides a better grasp of the history of Carthage. “The archaeological evidence suggests that the earliest colony of the eighth to the seventh centuries bce was surrounded by a kind of ‘industrial belt’ outside the walls, consisting of workshops and metalworkers’ furnaces . . . installations devoted to working the murex to obtain dye, and to potters kilns” (Aubet 2001, 219). The earliest evidence for Carthaginian iron-working thus dates from the 8th to the 7th centuries bce, synchronous with or later than in sub-Saharan Africa.
The Multiple Origins Hypotheses
At their initial formulation in the 1950s and 1960s, the multiple origins hypotheses were essentially a reaction to the then dominant diffusionist explanation of the emergence of African metallurgies (Diop 1968; Lhote 1952). The reasoning was articulated on two main variables: the virtual ubiquity of iron ore in Africa, and the phenomenal diversity of metal production technology, techniques, and installations. M. L. Diop’s (1968, 27) summary of the debate is particularly interesting: “It is thus proven today that traditional iron metallurgy is very old, widespread, and autochthone to Africa; however, the cradles of this metallurgy still need to be identified, their chronology worked out more securely in order to delineate the hypothetic iron routes throughout the continent.”
The core of the issue revolves around the evolutionary model one relies on to make sense of the archaeological record. Proponents of the mid-1st millennium bce introduction of iron metallurgy to Africa rely explicitly on technological gradualism, with strong emphasis on prior familiarity with advanced pyrotechnology. Punctuated equilibrium models, not yet used in this debate, make more sense of sudden, unforeseen, and unpredictable bursts of creativity that may have resulted in multiple independent discoveries of metallurgical techniques. In fact, with evidence of early metallurgy experimentations in Serbia in the Balkans, the Anatolian plateau in Turkey, and India in southern Asia, the emergence of metallurgy was clearly a multicentric phenomenon (Chirikure 2014).
Archaeologically speaking, Africa is a large, under-researched landmass with, however, significant variations between regions. The probes sunk into the past of this continent are comparatively few, generally small in size, widely scattered, and limited in their coverage of past technological change. This having been said, it is worth restating the obvious: scientific assessments of the state of the art in any research field are by definition provisional syntheses deemed to further falsification. Different areas of Africa have been more or less intensively explored (figure 1). The chronologies of these different metallurgical traditions are available in numerous publications and will not be repeated in detail here (Bisson et al. 2000; Bocoum 2002; Chirikure 2015; Clist 1989; de Barros 2003, 2006; de Maret 2002; Deme 2003; Deme and McIntosh 2006; Essomba 1992, 2002; Eze-Uzomaka 2008, 2009; Grebenart 1985, 1988; Holl 2009c; MacEachern 1996; Okafor 1993, 2002; Okafor and Phillips 1992; Quechon 2002; Tylecote 1975; Zangato and Holl 2010).
The current research on African early metallurgies went through cycles of acceleration and slowdowns. The first growth spur happened in the 1970s and 1980s with the remarkable discoveries of N. Lambert (1975, 1983) in Mauritania, the surveys and test excavations conducted by Quechon and colleagues (Person and Quechon 2002; Quechon 2002; Quechon et al. 1992) in the Termit massif, and D. Grebenart (1985, 1988) in the context of the Programme Archeologique d’urgence de la region d’In Gall—Teggida-n-Tesemt). In addition, Essomba (1993) and Clist (1989) provided good summaries on the archaeology of metallurgy in Central Africa in the 1980s. They reviewed the material collected from sites in the Saharan and Sahelian part of the Chad Republic and the rainforest in Southern Cameroon and Gabon. The discoveries from Taruga and Samum Dikuya in the Nigeria Nok Culture area and the more accurate reassessment of the antiquity of the Meroe iron industry opened the gates for a totally new perspective on the genesis of African metallurgies (Echard 1983; Haaland and Shinnie 1985; Tylecote 1975).
That first spur was followed by a period of critical evaluation (Killick 2004; Killick et al. 1988; McIntosh and McIntosh 1988). A reassessment of Niger furnaces’ radiocarbon dates showed a handful of dates to be erroneous. This fact prompted Killick et al. (1988) to assert that “the only positive evidence for metallurgy for this region . . . is a single radiocarbon date of 1710 ± 110 bc (Gif 5176) for a copper-working furnace. . . . We suggest that this date be viewed with great caution until it can be corroborated by another method such as thermoluminescence dating of the fired lining of the furnace. . . . Until these are available, the evidence for metallurgy in Niger prior to 1000bc remains in doubt.”
The second growth peak occurred in the 1990s and 2000s after the rejection of unexpectedly early radiocarbon dates of furnaces installations in the Termit massif, the In-Gall Teggida-n-Tesemt area, and the southern Cameroon rainforest. New research was launched in the Termit massif (Quechon 2002; Person and Quechon 2002), with the explicit goal of collecting high-quality samples for radiocarbon dating. Organic temper was extracted from pottery, charcoal samples were collected from the furnaces, and date accuracy was assessed comparatively (i.e., when pottery dating was coherent with furnace dating). The stunning discoveries of an original iron-smelting tradition in the Nsukka area of Nigeria (Okafor 1993, 2002), the finds from northern Mandara (MacEachern 1996), as well as Zangato’s (1999) research in the northwestern Central African Republic were parts of this new research round. This new wave of fieldwork confirmed the trends that emerged from the first growth spur. Iron metallurgy appears to date between 2000 and 600 bce in all these four study areas.
The third round is going on right now (in the 2000s forward). Archaeological research on early metallurgies has witnessed a number of interesting and surprising discoveries in the last decades. New work at Walalde in Morphil Island in the Middle Senegal Valley has revealed an early iron smelting tradition dating to c. 800 to 550 bce (Deme 2003; Deme and McIntosh 2006). The excavation probe did not contain any direct evidence of iron smelting installation. Forty seven tuyère fragments and 19 km of slag were collected, suggesting that an iron-smelting workshop was very likely present nearby but somewhat out of the scope of the excavation probe. The analysis of smelting debris points to furnace temperatures ranging from 1200oC to 1300oC (Deme and McIntosh 2006, 336; Killick 2016).
Sustained fieldwork, to be discussed in more details later (see “Horticulturalists of Eastern Adamawa”), resulted not only in the confirmation of prior findings but also in the discovery of still older iron processing facilities at Oboui and Gbatoro in the eastern extension of the Adamawa plateau in Cameroon and Central Africa, dated to c. 2200–1965 bce (Zangato 2007; Saliege 2007, 135). Research at Dekpassanware in north central Togo (de Barros 2003, 2006) also produced unexpected results. The 30-ha site has a 1.80-m to 2.10-m thick archaeological deposit. The bottom sequence accumulated between c. 800 and 400 bce is a Late Stone Age occupation. The top segment is a Late Iron Age occupation dated to 1300 and 1600 ce. The intermediate deposit containing slag concentrations, iron ore, tuyères fragments, and poorly preserved iron artifacts belongs to an Early Iron Age occupation. It accumulated between c. 400 bce and 100 ce, “1000 years older than expected” (de Barros 2003, 75). Bena, at 12o 04’ 05” N and 4o 11’ 02” W in the Bwamu in Western Burkina Faso, includes a series of natural draft semi-subterranean furnaces dated to 360–220 bce (Coulibaly 2006; Kiethega 2006). And finally, new evidence from the Senegambian megaliths brings additional interesting data to the puzzle of African metallurgies (Holl and Bocoum 2013, 2017). Tumulus SN-T-01, a single burial mound dated to 848–992 Cal bce (ISGS-7227), contains the remains of a 25- to 30-year-old male buried with an exceptional series of artifacts (figure 2): (1) a thin and delicate copper torque with a biconical pendent; (2) an iron sword—probably in a leather sheath—across the chest; (3) a set of eight iron spearheads on the left shoulder; (4) an iron “walking stick” handle; (5) an iron “fly-whisk” handle; (6) a belt buckle in alloyed copper; (7) a pair of iron tokens at the ankles; and (8) a finely made ankle ring in alloyed copper (Holl and Bocoum 2017, 129–130). The second case dated to 1362–1195 Cal bce (Dak-1457) consists of a “highly choreographed” collective primary burial of four individuals in a “stone-ringed tumulus” (figure 2). “A carnelian bead and an iron spearhead with bent tip were found embedded in the remains, with the latter underlying the skull of the upper individual (Holl and Bocoum 2017, 186).
Looked at from a broader continental perspective, these new discoveries add significantly to the intriguing puzzle of the origins of African metallurgies (Bisson et al. 2000; Bocoum 2002, 2006; Herbert 1993; Holl 2009a, 2009b; Holl and Bocoum 2013, 2017; Pringle 2009; Zangato 1999, 2007; Zangato and Holl 2010). The Niger, Nigeria, Cameroon, and Central African Republic early iron-producing sites all point to diverse craft traditions that started to develop at the middle-end of the third millennium bce.
The Copper Metallurgy Prerequisite?
The debate on the origins of African metallurgies was initially anchored on the “impossible” shift from Late Stone Age technologies to iron metallurgy. Such a situation made the diffusion from Middle Eastern centers more plausible. The discovery of copper metallurgy in the Akjoujt region in Mauritania (Lambert 1975, 1983) and the Eghazzer basin (Grebenart 1985, 1988; Bisson 2000) dated to the second and early first millennium bce shook the foundation of that consensus. In all the other areas reviewed in this article, however, iron metallurgy was adopted directly by Late Stone Age mixed-farming and horticulturalist communities.
A general outline of the origins of African copper metallurgy is presented by Bisson (Bisson et al. 2000). Native copper was exploited for one to two millennia. “The mining and smelting of copper ore appears to have arisen independently in Asia Minor, Eastern Europe, and Egypt between 5000 and 4000 bc” (Bisson et al. 2000, 88). He outlines a number of elements suggesting a link between the Akjoujt copper metallurgy, Western Europe Early Bronze Age, and Phoenician North Africa. First, the large proportion of utilitarian objects tends to suggest that copper technology was introduced in the area as a package, in contrast to all cases of early metallurgy development in which status objects are dominant. Second, there are striking stylistic similarities between Mauritanian, North African, and Iberic Peninsula copper artifacts. He concludes that “. . ., the presence of more prosaic copper artifacts at the beginning of the Mauritanian sequence suggests that the technology may have its roots elsewhere.” (Bisson et al. 2000, 90). As shown later (see “Objections and Refutation”), the cases from the Eghazzer basin that point to the late third–early second millennium bce age of copper smelting are still strongly debated (Bisson et al. 2000; Grebenart 1985, 1988; Holl 1997, 2000; Kense 1985; Killick et al. 1988). Egypt was suggested as the most likely initial source of the Eghazzer copper metallurgy:
It is not inconceivable that communications, however indirect and periodic, between the Nile Valley and interior Sahara regions occurred over a long period and that the knowledge of working with metals (particularly copper) was along the numerous routes to the west, southwest and south. Iron technology may have been introduced along similar networks by the turn of the first millennium bc, although additional stimulus was provided by the new links to the northern coast.(Kense 1985, 24).
Technology as Field of Interaction
A blunt but crucial question deserves to be formulated at this junction. How and why do technological invention and innovation occur? “An invention is a unique or novel device, method, composition or process,” while innovation can be defined simply “as a new way of doing things” (Mavhunga 2014). There is, however, significant overlap between invention and innovation. The initial discovery of a “transformative” action on natural matter was very likely serendipitous, an unintended by-product of another activity. Such an accident could trigger and channel the curiosity of some individuals or groups, be submitted to successive “experimentations,” and result in failure or success. However, an invention or innovation has to make “social sense” and find its “niche” in the social fabric to succeed, spread, and last. In many cases (e.g., gunpowder, cars, trains, planes, laser, computers, the internet), there are long time lags between the initial invention or discovery and the generalized use of the derived products:
One finds striking evidence of early experimentation with several copper minerals at Cayonu Tepesi (near Ergany, Turkey) in a seventh millennium context. Mining of copper took place with stone mauls and birch-bark baskets in the upper Great Lakes in the fifth millennium bc and with stone hammers and deer antlers at Rudna Glava in Eastern Serbia in the fourth millennium bc.(Wertime 1973, 879)
What happened during these time lags? These initial technological innovations, conducted very likely on a trial-and-error basis, independently in different sociocultural contexts, solved a local problem but did not spread. In fact, the complete social and economic value of an invention or innovation is often unpredictable at its initial stage, even within modern advanced technological societies (Adams 1996; Latour 1993; Lemonnier 1993). Technology is always imbedded in social systems. The advent of new technology can create new and unsuspected social demands or satisfy preexisting ones:
Techniques appear quite arbitrary from the standpoint of their physical adequation to specific effects on matter. And one crucial aspect of this arbitrariness seems to be that it finds its own logic in the production of what is called (for want of a better term) “meaning.” By classifying and interpreting what constitute their social and material environment and notably the relations they carry on with other individuals and groups, people confer meaning on the world they live in . . . . Men put meaning into the very production of techniques as well as make meaning out of existing technical elements.(Lemonnier 1993, 17).
Craft specialization thus develops in constant feedback with social demands. Initially and in virtually all cases, such demands are narrow and specific, geared to satisfy a small segment of the society. After a stasis, they change with time and expand, to encompass the society as a whole. In the case of metallurgies, it is at this final stage that “utilitarian” models are applicable.
Modeling Metals Production and Use
Metal production can be conceived of as a technological system made of diverse components in permanent and patterned interaction. Knowledge, know-how, and skills—the software—are the core parameters of any technological system. The physical environment provides raw materials: metal ores, clay, and fuel. The climate constrains the production calendar and influences the scheduling and timing of metal production. Different forms of social arrangements and labor allocation may generate part- or full-time specialization, sustain a minimal social demand for the manufactured metal products, support a more or less extensive distribution network, and feed varying patterns of consumption. A simplified flow chart model of metal production can help set the stage for the identification of key archaeological features and contexts (figure 3).
Ores, clay, and charcoal are mandatory raw materials for metals production. The procurement stage can be divided into three components for each of the required raw material. The search and identification of good-quality metal ores is a knowledge-demanding and laborious process. Metal ores can be found as veins underground, accessible through elaborate systems of shafts and galleries, or on the surface as cobbles or in sedimentary deposits. The collected ore is processed to facilitate its smelting in especially built features. It can be broken into small pieces and roasted to remove excess humidity. Clay and other refractory material like kaolin or recycled iron slag are used to build the furnace, the combustion feature in which the smelting takes place. Clay can equally be collected from pits dug in specific geological deposits or from sedimentary surface formations. The production of charcoal is equally knowledge demanding and labor-intensive. It involves the selection of the optimal kind of wood, the chopping of trees, and the manufacture of charcoal in specially made installations. An accurate assessment of the amount of fuel needed for a successful smelt is absolutely essential for the success of the operation.
The smelting operations take place in a special locality—the smelting site—where the furnaces are built. These combustion chambers vary in size, shape, and technical characteristics. They are generally cylinder-shaped with a more or less elongated chimney. Some are operated with blowpipes [tuyères] and bellows and others are natural draft installations taking advantage of wind power. They are filled from the top with alternating layers of ore and charcoal, lighted from the furnace mouth at the bottom, and, depending on their nature and size, can be operated for days by alternating crews of workers. A metal bloom made of metal—copper or iron—and slag is obtained at the end of each successful smelting episode. The bloom is then transferred to the blacksmith workshop where the metal is used for the manufacture of artifacts. The situations vary enormously from society to society. Blacksmiths can work on demand, the “customer” providing the bloom to be used for the manufacture of the requested objects. The blacksmith can also be an “entrepreneur,” manufacturing objects to be sold and channeled through a distribution network. The consumption and use of metal artifacts take different forms. Some are lost, other discarded, still others are buried with their owners, and depending on circumstances, certain worn-out pieces are recycled to save the precious material.
Metals production is generally a team effort, with experienced craft people training younger apprentices. The archaeological correlates of the model just outlined are straightforward. Mining shafts and pits can be found in the landscape. Charcoal-making installations—burnt surfaces—are more ambiguous and difficult to identify. Smelting furnaces, forge furnaces, and other installations are easily identifiable. Beside burials and special caches, contexts of use like houses or courtyards are difficult to pinpoint.
Objections and Refutation
The debate on the genesis of African metallurgies is—rightly at this point—narrowly focused on a handful of important issues—dating techniques, site integrity, iron artifacts preservation—that need to be addressed (Chirikure 2010; Craddock 2010; Eggert 2010; Killick 2015, 2016a, 2016b; MacEachern 2010; McIntosh et al. 2016).
The reliability of radiocarbon dates in research on early African metallurgies is contested by some researchers. For Killick et al.(1988), the “old wood” problem is “so pervasive that any attempt to infer the origins of metallurgy in Africa from the present radiocarbon base should probably be suspended” (in McIntosh and McIntosh 1988, 106). The old wood problem, initially identified in Southwest United States Hohokam archaeology (Schiffer 1986), does not apply to tropical Africa vegetation and iron production. Charcoal from natural fires, which is hard to identify at first glance, can effectively “contaminate” metal smelting installations. The fuel used in iron smelting is not picked at random from nature waste. It is obtained from selected wood species and processed for optimal efficiency.
A complementary aspect of the rejection of radiocarbon dates is presented by McIntosh and McIntosh (1988, 107). It stemmed from the availability of a high-precision calibration curve for the years 2500bce to 1950ce: “The dramatic flattening to the calibration curve in the mid-first millennium bc means that the majority of the dates for early metallurgy in West Africa cannot be resolved to better than 800–400 bce” (McIntosh and McIntosh 1988, 107). It is consequently assumed that all early cases of African metallurgies date from the middle of the first millennium bce, a time segment characterized by erratic fluctuations of atmospheric carbon, a situation making any precise chronological assessment impossible. Logically and for coherence sake, if the “flatness” of the calibration curve is confined to the 800–400 bce time segment, dates of metallurgical installations older than 800 bce and younger than 400 bce should be accurate. Considering the rather loose archaeological coverage of Africa, the scale and resolution of surveys, and the sheer number of excavations that need to be done, one would expect scientists to be open-minded because so little is known (Holl 2009c). The speculative 500 bce baseline for the emergence of African metallurgies has no sound empirical grounding.
Another class of objection revolves around systemic archaeological site perturbations. Bernard Clist (in Pringle 2009) surprisingly referred to generic extensive post-depositional disturbances in Central Africa archaeological sites to dismiss the unexpected results from Oboui in the Central African Republic. Such a blanket statement flies in the face of evidence. It is clearly the weakest argument in the whole debate, dismissed without further consideration by Eggert (2010, 37–38) and Craddock (2010, 33) as follows:
It has been argued that the stratigraphy of both cases [Oboui and Gbatoro] was complex with opportunities for mixing, but it is difficult to envisage the scenarios in which smithies, which by the nature of their operations should leave copious quantities of charcoal, should have survived as entire archaeological features but have their charcoal replaced. Both areas are believed to have been wooded at the supposed time of their operation and so the problem of the use of ancient wood should not arise.(Craddock 2010, 33)
It is possible to track site perturbation in any carefully conducted archaeological excavation. The samples used for dating purposes are carefully selected from secure, reliable, and controlled archaeological contexts.
And finally, the last class of objection focuses on the relatively good state of preservation of metal items from Oboui: “The recent publication of an undoubted iron forge with radiocarbon dates around 2000 Cal bc at Oboui (Central African Republic) seemed to prove that iron was first smelted in Africa (. . .). The excavators obtained seven consistent radiocarbon dates calibrated (at 95 percent probability) in the range 2343 to 1900 Cal bc, but subsequent commentators have noted several puzzling anomalies. The blooms and forged artifacts from Oboui are quite well preserved, retaining substantial amounts of metallic iron, but iron that has sat for 4000 years in an open site in the tropics should be fully corroded” (Killick 2016, 68). The hyperbolic expression “sat for 4000 years in an open site in the tropics. . .,” clearly intended to impress the reader, is at variance with the carefully investigated and well-dated stratigraphy of Oboui (Zangato 2007). In fact, the evaluation of the state of preservation of Oboui iron artifacts is based on published illustrations. This objects sample was effectively selected for publication because of its relatively good preservation out of 174 iron artifacts and by-products collected from Oboui forge. The objection has no merit.
Addressing technicalities is important but the “tree does not have to hide the wood.” Metallurgies have to be analyzed within the global archeological contexts to which they belong. A holistic approach, anchored on the political economy of metallurgy, can help retrieve parts of the emic dimension of past societies as well as the relative values they assigned to metal artifacts in their actual cultural universes. Research freezes or moratoriums are not helpful. Relying on Popperian conjecture and refutation rationale, pragmatic research requires the use of the data available to address the issue at hand. The conclusions reached today may be confirmed or refuted in the future. Four case studies are selected to showcase the potential of such a holistic approach. The presentations are strongly evidence-based to address the objections raised in this ongoing debate.
Pastoral-Nomadic Societies of the Eghazzer Basin, Niger
The Eghazzer basin is located between the Air mountain, the Tiguidit cliff, and the Azawagh in Niger Republic. It is a relatively flat flood plain with an interesting resources spectrum: (1) prime grazing land with natural fields of Sorghum eathiopicum [wild sorghum] and Panicum laetum; (2) brackish springs and salt accumulation areas; (3) copper ore along fault lines; and (4) iron ore, especially in the Tiguidit cliff (Grebenart 1985, 1988; Poncet 1983; Holl 1997, 1998, 2004, 2009c). Considered from the vantage point of a “whole resource package”—soils, pastures, wild grain, salt, water, game, fish, copper, and iron—one would expect site location strategies to be geared toward optimal and timely exploitation of the Eghazzer basin potentials. This optimal exploitation, operating as embedded procurement, was articulated on seasonal moves from one part of the basin to another, depending on the availability and timing of key resources. The richness and overall predictability of the Eghazzer basin resources have triggered attempts at territorial marking through the use of cemeteries and monumental burials. The invention or adoption of copper and iron metallurgy took place in this context of the emerging mobile pastoral elite (MacDonald 1998) in an area with abundant highly productive natural fields of Sorghum aethiopicum and Panicum leatum. There is convincing evidence of the practice of cattle sacrifice. Some individuals are buried with lambs (Paris 1984). The pastoral-nomadic nature of the Late Holocene societies of the Eghazzer basin is not disputed. The combined regional distribution of Late Stone Age, Copper I, Copper II, Early Iron Age, and megalithic cemeteries presents a number of striking regularities (figure 4).
Large cemeteries are all located in the optimal zone of the basin (table 1, figure 5). Shin Wasadan, Tuluk, and Anyokan are equidistant, located at 50 km from each other. Asaquru in the northwest and Asawas in the southeast are found at 15–20 km from Shin Wasadan for the former and Tuluk for the latter. The remaining cemeteries, arranged into Rank II (20–99 burials), Rank III (5–19 burials), and Rank IV (1–4 burials), are differentially scattered around Rank I (>100 burials) localities. The build-up of the cultural landscape of the Eghazzer basin was a cumulative process (figures 4 and 5). It started during the Late Stone Age (c. 4000 bp) and lasted up to the influx of Ancestral Tuareg and Islam in the second half of the first millennium ad. The territorial entities delineated by the distribution of megalithic burials and cemeteries were probably in a constant state of flux (table 1). They nonetheless signal the existence of five interacting relatively large pastoral nomad “confederacies” in the Eghazzer basin (Holl 1998, 155–157; Holl 2013).
Table 1. Spatial Organization of the Eghazer Basin Megalithic Cemeteries
1 (> 100)
Anyokan (IG 2)
Asawas (AG 31)
Tuluk (TTA 44)
Shin Wasmlan (TTA 16)
Asaquru (TTS 48)
4 (AG 30, IG 21, 23. 32)
12 (AG 32, 33, 34, 39, 62, 73, 75, 106, 108, 109, 117)
12 (TTA 25, 26, 28, 32, 33, 35, 40, 41, 42, 47, 51, 52)
8 (TTA 4, 7, 9, 15, TTS 9, 10, 11, 31)
6 (TTS 3, 38, 49, 53, 74, 88)
I (IG 27)
2 (AG 35, 53)
3 (TTS 2, 80, 82)
4 (TTS 75, 83, 92, 93)
Burial grounds were accordingly used to “root” these ever-changing groups in the landscape, with the largest central cemeteries used as a focal point for the scattered communities belonging to each of the five “tribal networks.” New materials, like copper and later iron, were adopted without significant change in the basic lithic toolkit (Grebenart 1985). A total of 309 sites, 148 for the Late Stone Age, twenty-six for Copper I and II, nineteen for Early Iron Age, 103 megalithic cemeteries, and thirteen undetermined, were recorded in the Eghazzer basin. Habitation and smelting sites distributions vary from period to period. Late Stone Age sites were predominantly located on the periphery of the central clayey depression of the basin (figure 4). Thirteen LSA sites were tested. With the exception of large cemeteries (Anyokan, Asaquru), they tend to be small in size, measuring 0.12 ha to 2.40 ha (Holl 2004, 129; Holl 2013). Three of these sites: Afunfun 161, Afunfun 176, and Chin Tafidet, dated to 3400–3000 bp, have evidence of animal sacrifices and combined human and livestock burials (Paris 1984). Such data point to the existence of pervasive pastoral ideology.
Most of the sites with evidence of copper are confined to the northwest along the Eghazzer River. Ten of the tested Copper I and II sites range in date from 4100 to 2400 bp (figure 4). They are distributed into small camps and villages and tend to be larger, measuring 0.03 ha to 20 ha in size. Afunfun 162, Afunfun 175, Ikawaten, and Sekkiret were copper smelting sites with hundreds of furnaces arranged in batteries. Copper I smelting furnaces dating from c. 4000 to 3000 bp are extremely diverse in size and shape (figure 6).
Such a diversity, which has puzzled typology-minded researchers, makes sense if viewed as the “signature” of a long and uneven period of trial and error. The data point to an uncertain “experimentation” phase that led to the development of best-fit copper smelting devices. Copper II furnaces present a certain amount of variations, but they are all more or less cylindrical in shape (figure 7), some with a small bottom pit reminiscent of a “medicine pot,” frequently recorded in different parts of the continent (Schmidt 1996, 1997; Schmidt and Mapunda 1997). The smelting of metals is conducted through and accompanied by intense ritual activities and taboos (Childs 2000; de Barros 2003; Herbert 1993). The deposit of “medicine” in a pot or a small pit at the base of the furnace aims to protect the smelt from adverse “malicious” forces.
Sites with iron metallurgy are found in the south, essentially along the Tiguidit cliff. The nine tested localities are dated from c. 2600 to 2100 bp. They range in size from 0.5 ha to 3 ha, with three, Ekne wan Ataram, In Taylalen II 15, and Teguef n’Agar, containing iron smelting furnaces (figure 8).
Megalithic cemeteries, the defining elements of the cultural landscape, are distributed all over the basin (figure 5). Metal artifacts were collected from habitation, smelting sites, and megalithic burials. The artifact sets from habitation and metal-producing sites are more diverse and heterogeneous. Stone tools were still in use for daily activities. Metal tools useful for productive tasks are almost absent from the collected assemblages. This absence is ambiguous. Such tools could have been highly curated and, when worn out, recycled. In any case, the recorded sets of metal implements resulted from palimpsests of multiple occupation episodes, through loss and discard of worn-out artifacts. Burial assemblages present a narrower range of artifacts, in this case, items of personal adornment and weapons. The former are preferentially in copper and the latter in iron. The recorded pattern of metal “consumption” suggests a consistent and long-lasting hierarchy of metal goods generated and sustained by subtle patterns of social demands. In this perspective, items of personal adornment and iron weapons seem to have been manipulated in tactics and strategies of social distinction (Bourdieu 1979).
Mobile Herders from the Akjoujt Region, Mauritania
N. Lambert (1975, 1983) conducted an intensive research project in the Akjoujt region of Mauritania. She carried out surveys and excavations in the Guelb Moghrein, at three distinct nodes of the metal production and use system. She investigated copper ore mining at the cave site of the Grotte aux Chauve-souris. The formation and the extension of the cave itself resulted from the exploitation of copper ore. The obtained ore was processed at the Lemdena smelting site in small bowl-shaped furnaces. And the Lembatet-El-Kbir cemetery provided evidence for the kind of artifacts regularly manufactured and buried with the deceased. The small smelting furnaces recorded at Lemdena and the material from the Grotte des Chauve-souris range in date from 826 ± 126 (Dak 25) to 400 ± 110 bce.
Convincing evidence of copper metallurgy dating from c. 800 to 300 bce, if not, earlier was thus documented in the Akjoujt region of Mauritania. It is worth noting that older radiocarbon readings obtained from the same area and pointing to 1100–810 bce (2776 ± 126 bp) and 990–790 bce (2700 ± 110 bp) time range published by Willet (1971) were rejected by the excavator “as being too old in relation to the other material from the sites” (Woodhouse 1998, 173). The Akjoujt region copper metallurgy was geared toward the production of small-size implements: weapons, such as spears and arrowheads; tools, such as burins, borers, axes, needles, sticks, and palettes; and items of personal adornment, such as arm rings and finger rings. Most of the mining pits, smelting sites, and features were located along the Amatlich. Copper artifacts from the Akjoujt region were found in settlements located in western Mauritania, in the north of Nouakchott, and further in the southeast along the sandstone cliff of Dhar Tichitt-Walata (Vernet 1986, 36–37). The excavation of a dune site at Khatt Lemaiteg (Bathily et al. 1992) produced surprisingly early copper artifacts in “Habitation 2,” dated to 1890–1390bce (3310 ± 200 bp). They consist of projectile points, an arm ring, and stone beads attached to a wire loop, all said to be “in the same style as objects found at Akjoujt” (Woodhouse 1998, 173). For the excavators, however, these artifacts were intrusive to the site (Bathily et al. 1992). In Mauritania, the frequent association of Late Stone Age material—pottery, grindstones, grinders, and axes—and copper artifacts has puzzled researchers for a long time. In contrast to what could be expected from the “utilitarian principle” perspective, the development of copper metallurgy did not trigger any radical and visible change in the material culture repertoire of Late Holocene inhabitants from the Akjoujt region. For Vernet (1986, 37), for example, the “metallurgist folk from Akjoujt are unknown.”
The case study from the Akjoujt region is particularly enlightening. At the beginning of the first millennium bce, and very likely earlier, new techniques of copper production were adopted without visible parallel transformations in the rest of the material culture repertoire. The new craft filled a specific social niche and generated an extensive distribution network of copper artifacts. Around c. 300 bce, however, the whole system collapsed and vanished from the archaeological record. Beyond the production area stricto sensu, where mining pits and smelting workshops with low furnaces were recorded, most of the copper artifacts were collected from so-called Neolithic contexts.
The difficulties in the identification of Akjoujt “metallurgist folk” are linked to two main factors: the palimpsestic nature of the studied settlements that are shallow surface sites with scattered pieces of material culture; and the taxonomic system based on a succession of “Ages” used to make sense of the archaeological record. Stone tools belong to the Stone Age. Copper artifacts belong to the Copper Age. Stone tools and copper artifacts do not mix. If this happens, the latter are intrusive in the context of the former. Data from the Eghazzer basin, as discussed, are an effective refutation of such a typological view.
The systematic occurrence of copper artifacts in contexts with stone tools and pottery is very likely an accurate rendering of the past. With the advent and adoption of copper metallurgy, the Akjoujt region late Holocene mobile herders witnessed the development of patterned divisions of labor, resulting in the emergence of craft specialists. These craft people probably operated on a part-time basis, manufacturing highly valued copper objects that were channeled through an extensive exchange network. Ore procurement, smelting, forging, and distribution were imbedded in the regional pastoral-nomadic groups’ subsistence-settlement systems. It can be inferred that the procurement and smelting of the copper ore took place during the seasonal sojourn in the Akjoujt and Bir Moghrein areas. Forging, artifacts production, and distribution were organized during the rest of the year, during complementary rounds of seasonal moves from camps to camps. Artifacts may have spread through down-the-line exchange between neighboring groups. If looked at from the perspective just outlined, the distinction between “metallurgist folks” and the “Neolithic people” loses all its salience; these were in the spectrum of different facets of activities of the Akjoujt region late Holocene pastoral-nomadic communities.
Horticulturalists of Eastern Adamawa
They took advantage of the ecotonal richness of the forest galleries along the multiple rivers from the Chad and Congo catchments. Hunting, fishing, and the gathering of wild plants were the main components of their subsistence. The remains of palm oil nuts [Elaeis guineensis] and Canarium schweifurthii are frequent in the excavated sites. The area is particularly rich in wild yams with aerial and underground tubers. Evidence of agricultural practices is still lacking but agroforestry is suggested by the constant presence of oil palm endocarps. Intensive exploitation of wild yams that may have led to the domestication of African yam—Dioscorea cayenensis—is a genuine possibility. As is the case in the Eghazzer basin, megalithic monuments were built and used as territorial markers (Zangato 2000). They are generally located at or near the source of water courses, part of a very dense hydrographic network. Craft specialization led to the formation of iron-working individuals or groups at the end of the third and beginning of the second millennium bce among these settled horticulturalists (table 2 and figure 10).
Table 2: Radiocarbon Dates of the Early Iron Working Sites from the Eastern Adamawa
Oboui blacksmith workshop
3645 ± 35
3635 ± 35
3665 ± 30
3675 ± 30
3690 ± 40
3995 ± 40
Gbatoro blacksmith workshop
3707 ± 29
3835 ± 30
Gbabiri smelting site
Layer 3 h2
2630 ± 40
Layer 3 h1
2670 ± 40
2680 ± 40
Gbabiri blacksmith workshop
2640 ± 40
Balimbe habitation site
2980 ± 40
3530 ± 40
Bounboun habitation site
3598 ± 30
Betume habitation site
4350 ± 30
(Calibration IntCal04 [Reimer et al. 2004])
Oboui: Late 3rd -Early 2nd Millennium bce Blacksmith’s Workshop
Oboui is a small residential site located at 6o 03’ N/15o 20’ E, at 1048 m above sea level (asl) in eastern Adamawa plateau. The tested excavation probe measures 800 m2 , with a 1.15- to 1.50-m thick cultural deposit (Zangato 2007; Saliege 2007, 135). The exposed archaeological sequence is made of three sedimentary units, each with two to three distinct horizons:
Sedimentary unit 1 is located at the bottom of the sequence with:
C1h1: a natural sedimentary deposit, light brown (75/10-YR 8/4), with numerous slate fragments delineated at its bottom by a thin layer of quartz flakes.
C1h2: a fine yellow-red (65/7.5-YR 6/6) silty sand 20-cm to 25-cm thick. It contains a small sample of stone tools assigned to the Late Stone Age and is capped by a harder sterile compact clay layer, 5–10 cm in thickness.
C1h3: similar to the underlying C1h2. It contained three ground axes, adzes, flakes, and a relatively large quantity of potsherds assigned to the Neolithic period.
Sedimentary unit 2, 0.20-m thick, seals the earlier deposit and consists of:
C2h1: a clayey sand, relatively coarse and compact, 5–9-cm thick. It is archaeologically sterile and sealed by the overlying gravel layer.
C2h2: a coarse gravel deposit with broken angular fragments of granite, quartzite-sandstone, and quartzo-laterite in a light yellow (77–2.5-Y 7/4) clayey sand matrix, 10 cm to 15 cm in thickness.
C2h3: made of the same sedimentary material as the previous C2h2, 5-cm to 10-cm thick, with frequent dark brown soil spots.
Sedimentary unit 3 is at the top of the archaeological sequence with three horizons.
C3h1: a sandy light yellow (77–2.5-Y 7/4) clay 35-cm thick. The deposit also includes dark-brown soil dots resulting from pits, hearths, and other features dug in overlying levels. The top of this level is fire-hardened by intensive iron-working activities. A series of seven radiocarbon measurements dates this deposit from 2343–2044 to 2135–1921 bce, to 121 ce
C3h2: a fine yellow-olive (N89/2.5-Y 6/6) sand, 15-cm to 20-cm thick, contains a significant number of archaeological features. A series of twelve radiocarbon readings dates this level from 383–121/39 bce to 121 ce (table 2)
C3h3: a 20- to 25-cm thick deposit of sandy and clayey topsoil. A series of five radiocarbon readings dates this level from 39 bce/121 to 346–544 ce.
A series of iron-working installations were exposed in horizon C3h1 (figure 11). All these features (6a to 6j) are part of an early blacksmith’s workshop, made of a number of complementary installations arranged around a central forge furnace. The workshop measures approximately 5 m in diameter and includes a number of installations, as well as scattered bloom fragments, iron wires, and rods.
The forge furnace (feature 6a) measures 100 cm in diameter (figure 11), delineated by granite slabs and a fired clay lining. The preserved shallow pit is 20–30 cm deep with two blowpipes, both found in the southwestern side of the feature. One of the blowpipes (tuyère), tronconical in shape, measures 22 cm in length, 15 to 9 cm in diameter, and 3–2 cm in wall thickness. Three charcoal samples were collected from the inner part of the forge furnace. The obtained radiocarbon dates range from 2140–1958 to 2132–1900 Cal bce (table 2).
A stone anvil in quartzite-sandstone, measuring 45 cm in diameter, was set on the northeastern flank of the forge furnace. A clay vessel (feature 6g) used for quenching was exposed abutting the forge furnace on its southeastern flank. Features 6d and 6e are charcoal pits located at half a meter away from the furnace, on its east side. Pit 6d is more or less circular in shape, measures 1 m in diameter, with depth varying from 25 cm to 50 cm. A charcoal sample dates the pit to 2135–1921 Cal bce (table 2). Pit 6e is slightly smaller, 0.85 m in diameter, and 25 cm to 30 cm deep. Pits 6f and 6j were very likely used for refuse disposal, both dated to 2343–2058 and 2200–1965 Cal bce. The former, located on the south flank of the forge furnace, measures 1 m in length, 0.70 m in maximum width, and 5 cm to 10 cm in depth. The latter, pit 6j is shallower, 3 cm to 7 cm in depth, circular in shape, measuring 0.90 m in diameter. The content of these refuse pits is particularly interesting as it includes thirty-four pieces of slag droplets, twenty-eight iron bloom fragments, nine fragments of oxidized iron wires, eighty-one hammerstone fragments, twenty-six potsherds, and several pieces of furnace walls. A hearth (feature 6h), located at the southwest end of the forge workshop, is dated to 2198–1959 Cal bce (figure 11). It is a cluster of burnt granite blocks, ash, large charcoal pieces, and burnt wall fragments. The cultural remains collected around feature 6h include twenty-seven potsherds, nineteen fragments of droplets, twenty-six iron bloom fragments, and eight pieces of cut iron wires. Finally, feature 6i, at approximately 1 m northwest of the forge furnace, measures 0.80 m long, 0.25 m wide on the average, and 10–15 cm deep. It is filled with a sediment rich in organic material, small charcoal fragments, and numerous remains of burnt Burseraceae endocarps, as well as three stone artifacts found in the pit bottom, including two stone adzes and one blade.
A number of iron-working by-products and iron fragments were found scattered all over the workshop (figure 12). They include twenty molten slag pieces, one bottom slag, forty-five iron wires fragments, seventeen pointed iron fragments, sixty-five flat iron pieces, fifteen round iron pieces, ten angular iron pieces, and two iron needles. In general, the recorded iron artifacts can be arranged into ten thickness classes, ranging from 7 to 16 mm. Wires fragments and flat pieces make up to 78 percent of the recorded iron artifacts, with thicknesses ranging from 7 to 10 mm.
The data obtained from the excavation so far offer interesting insights into all aspects of the chaine operatoire of iron production but the initial mining and iron ore smelting. The site was used, very likely on an intermittent basis, between 2340 and 2058bc and 1900bce. The recorded early artifacts range from needles to blades, with unidentified iron fragments. The analysis of slag samples attests to high-performing smelting installations with a very small amount of lost iron. The dendritic pattern of ferrite crystallization points to high furnace temperatures that may have reached 1536oC (Fluzin 2007a, 60). And the main technique of artifact manufacture appears to have been hot-hammering combined with quenching (Fluzin 2007b, 72).
The blacksmith workshop discovered at Oboui is particularly coherent in chronological and functional terms. The recorded installations include a forge furnace (features 6 a–d), a stone anvil for hammering the bloom, a clay vessel for quenching purposes (feature 6g), two charcoal storage pits (features 6d and 6e), three refuse pits (features 6f, 6i, 6j), and finally, one hearth (feature 6h). All steps of the forging chaine operatoire are represented in the excavated workshop. All the dated samples point to the same time segment, between 2300 and 1900bce.
Gbatoro: A Late 3rd Millennium bce Blacksmith Workshop
Gbatoro is a small 2 ha site located at 1200 m asl in the Djohong area in Cameroon, at some 100 km at crow flight from Oboui. The site presents a 2 m thick stratigraphy made of four sedimentary units spanning from the Late Stone Age to the iron-using periods.
These sedimentary units were accumulated on a sterile natural clay layer.
C5: a sterile clayey natural layer;
C4: a 20- to 30-cm sandy layer with gravels sealed by an overlying sterile horizon containing Late Stone Age material;
C3: a 30- to 40-cm light brown-yellow clayey sand with gravels and a few granite blocks. sandwiched between a sterile clayey horizon at bottom and a 5- to 10-cm thick gravel horizon on top;
C2: a 25- to 40-cm dark yellow sand sandwiched between a gravel horizon at bottom and a thin clay crust on top. It contains hundreds of large charcoal pieces and evidence of iron-working dated to 2153–2044 and 2368–2200 Cal bce; and
C1: a 20-cm brown-gray topsoil accumulated above a thin 2- to 3-cm thick clay crust.
The 110 m2 excavated probe revealed a blacksmith workshop in layer C2. The exposed workshop is roughly circular in shape, approximately 4 m in diameter (figure 13). As suggested by the distribution of iron-working features and by-products, this workshop was likely roofed, with the possibility of a surrounding low wall.
The forge furnace, dated to 2368–2200 Cal bce, measures 0.90 m in diameter, the depth ranging from 20 cm to 30 cm. The position of the single tuyère well delineated on the southeast flank is oriented NW-SE. The furnace pit filled with heterogeneous sedimentary material also included fired wall fragments and large charcoal pieces.
A refuse pit in which ash and burnt material from the furnace were dumped was exposed at 1.5 m southwest of the furnace. It measures 1.50 m in diameter and is dated to 2044–2153 Cal bce. Beside ash and charcoal, the pit fill contained a number of iron fragments as well as numerous potsherds.
The repertoire of cultural remains found in the workshop is remarkably broad. It includes 120 potsherds, three tuyères fragments, sixty-five bloom fragments, eighty-nine molten slag, thirty-six iron fragments, one complete iron artifact (figure 13), as well as heavy-duty coarse stone artifacts.
The tuyère fragments were found in the northeast flank of the furnace. They measure 10 cm to 18 cm in length and 6 cm to 7 cm in diameter. The heavy-duty stone artifacts are scattered all over the workshop. They are essentially hammerstones of different sizes in quartzite-sandstone. A few small-sized bifacial pieces, measuring 4 cm and 9 cm in length, 2.5 cm to 3 cm in width, and 1 cm and 2.2 cm in thickness, were also recorded. Good-quality milky quartz, the raw material used for the manufacture of these pieces, is of local origins, found in the quartzitic outcrop of the western slope of the dividing line between the river Lom and the river Mbere watersheds.
The bloom fragments are all concentrated in and around the furnace. There are two main clusters, in the south and northwest where portable anvils may have been positioned for hot-hammering. The Gbatoro blacksmith workshop does not have a quenching pot. Stone anvils were not found but the location of hammering “spots” is well indicated by the concentration of bloom fragments.
The material from Gbatoro presented in this article is preliminary in nature. The excavation of the site is not completed yet, as one may expect additional data in the northern side of the blacksmith workshop. In general, however, iron production activities were carried out at Gbatoro at the end of the third millennium bce, as was the case at Oboui 100 km further east.
Gbabiri: 1st Millennium bce Blacksmith’s Workshop
Gbabiri is an 8 ha village at 1080 m asl, 5 km north of Oboui. Two 200 and 300 m2 excavation units were set in the south and east (Zangato 2007, 67). Several smaller 1 × 1 m or 1 × 2 m probes and trial trenches were dug to assess the precise extent of the site.
The recorded stratigraphic build-up of the site is made of four main sedimentary units.
Sedimentary unit 1 is the bottom natural geological deposit supporting the cultural deposit. It includes a single layer;
C5: a natural dark brown sterile clayey sediment;
Sedimentary unit 2, the earliest cultural deposit, is subdivided into three layers sandwiched between two sterile clayey horizons;
C4: a 12- to 32-cm thick layer of weathered granite and clay, dated to 906–796 Cal bce;
C3: just above, is a less clayey and more homogeneous soil divided into two horizons: C3h1 immediately above C4 is dated to 902–794 Cal bce. C3h2 is sandwiched between two sterile layers. It contained a large amount of charcoal and is dated to 895–773 Cal bce. A blacksmith workshop with a forge furnace, a charcoal pit, and a large amount of material culture remains was found in this deposit;
Sedimentary unit 3, 30- to 40-cm thick, is divided into two horizons;
C2: a 30- to 40-cm thick deposit with moderately hard dark-brown soil. Both horizons share the same sedimentary profile: C2h1 is dated to 152 Cal bce–55 Cal ce; and C2h2 is dated to 39 Cal bce–121 Cal ce;
Sedimentary unit 4 seals the sequence and represents the last occupation of the site; and
Layer C1 is 30- to 45-cm thick, divided in two horizons, and overlain by topsoil. C1h1, the lower horizon, is dated to 242–403 Cal ce. C1h2, the upper one, is dated to 346–544 Cal ce.
This unit was relatively rich in archaeological remains, with the total of collected pieces amounting to 4,568.
The lower levels of an earlier iron-working phase, C3 and C4, were found and exposed over 110 m2 in level 3. The archaeological sequence of Gbabiri includes an early occupation level with a 12- to 32-cm thick cultural deposit dated to 906–796 Cal bce. As is the case for Oboui, this occupation level is sealed by a hard and compact brown-gray soil mixed with gravels extended all over both excavated units 1 and 2. The recorded cultural remains consist of 173 sherds, nine from smoking pipes (Zangato 2000), and 120 iron pieces. The latter are divided into seventy-five bloom fragments, thirty-two pieces of slag droplets, and thirteen slag fragments.
A later occupation level with evidence for intensive iron-working activities was exposed in the upper portion of layer 3. The recorded cultural deposit is 10- to 30-cm thick. The sedimentary material is a mix of weathered granite and clay, with a large amount of large charcoal pieces. A series of four radiocarbon readings dates this deposit to the very beginning of the first millennium bce, ranging from 902–794 to 895–773 Cal bce. Two interesting archaeological features, part of a small blacksmith workshop, were exposed in this deposit.
Feature 1 is located at the south angle of the excavated unit (figure 14). It is a relatively large pit measuring approximately 4 m2 and 13 to 18 cm deep. It contained a large amount of charcoal with ash concentrated along its southern perimeter. The collected cultural remains are made of fifty-seven potsherds, two hammerstones, twenty-three pieces of molten slag, and one relatively large bottom slag. The latter is a dense and heavy slag weighing 1.58 kg. It has a series of small cracks, imprints of charcoal, and pieces of iron ore on its upper side. The lower side is oxidized and bears traces of the underlying sediment. Pit 1 was very likely used initially for charcoal storage. It was recycled later into a refuse receptacle.
Feature 2 is located at 3.5 m north of the previous one (figure 14). It is circular in shape, measures 1.5 m in diameter, and 0.15–0.20 m in depth. The perimeter is delineated by a burnt clay wall and the interior was filled with a relatively large amount of charcoal. The radiocarbon reading dates feature 2 to 895–773 Cal bce. Two tuyères fragments, 5 to 8 cm long and 4 to 5 cm in diameter, were found inside the furnace base. A large and heavy 30 kg quartzite-sandstone piece set against the furnace wall was found on the west flank of the feature. The surface of the stone block is pitted, likely because of intensive hammering work, suggesting it was an anvil. The remains of a complete hole-mouth vessel measuring 25 cm in height and 36 cm in mouth diameter was found in a shallow pit on the south side of the furnace. The recorded ware, undecorated with straight sides, was used for quenching purposes.
In addition to the uncovered features, the excavation of units 1 and 2 has produced an interesting array of cultural remains: 136 iron bloom fragments, sixty-six droplets, fifty-five slag pieces, eighty-five fragments of iron sheets, one small knife blade, one bell, two iron spear or arrow stems, and two arrow points. The thickness of the iron sheets pieces found at Gbabiri is similar to that of Oboui; 65 percent of the recorded fragments measure 11 to 13 mm in thickness.
In summary, the uncovered blacksmith’s workshop is dated to 900–750 bce. In this case too, there is a forge furnace, an anvil, a few hammerstones, a quenching pot, a charcoal storage and refuse pit, slag pieces, clay smoking pipes, a number of iron artifacts, and a series of potsherds (Zangato 2007, 69). The chaine operatoire of this production process includes heating in the forge furnace, hammering on the anvil, quenching when needed in the quenching pot, and reheating, rehammering, and re-quenching as much as necessary to achieve a satisfactory result.
In general. a sample of 141 complete iron artifacts was collected during the northwest Central African Republic research project. Weaponry is largely predominant, with eleven out of eighteen represented functional categories (Zangato 2007, 118). It includes knives, spears, arrowheads, harpoons, and axes. Needles were probably used in craft activities, and rings point to personal adornment.
The iron-working traditions of northern Central Africa, found in part in Cameroon but better researched in Northwestern Central African Republic, emerged at the very end of the third and very beginning of the second millennium bce
Mixed Farming Mound-Dwellers of the Mouhoun Bend, Burkina Faso
The Mouhoun Bend Archaeological Project (NW Burkina Faso) was designed to investigate the development of food-producing economies in relation to Holocene climatic change and the emergence and amplification of craft specialization. The Mouhoun River (formerly known as Black Volta) flows from SW to NE, then winds its course in a U-shape bend to follow an almost N-S direction. The study area is delimited in the north and northeast by this meandering river course. The selected area measures 40 km east-west (3o 11’/3o 32’ longitude East) and 38 km north-south (12o 30’/12o 45’ latitude North). The land is flat in general, with elevation varying from 294 to 249 m above sea level. The vegetation is characteristically a highly anthropic wooded savanna, with the protected shea butter tree (Butyrospermum parkii) largely predominant, followed by different kinds of Euphorbiacea.
The results of three field seasons backed by a series of radiocarbon readings show the tested mounds to date from 700–600 bce to 1400ce (Holl and Kote 2000; Holl 2009b, 2014), with iron metallurgy present all along the whole sequence. The relatively rich local ethnohistory emphasizes large-scale migrations and population movements from the core of the 1200–1400 Mali Empire to the periphery where the study area is located. The Marka (a Mande-speaking nationality) are claimed to have been specialized merchants’ lineages [Dyula], involved in long-distance trade between the periphery and the core of the Ancient Mali. It is well known that there is no iron ore in the Inland Niger Delta (McIntosh and McIntosh 1980; McIntosh 1995; Togola 1996). Iron blooms and probably tools were imported from the surrounding lands. The Mouhoun Bend may have been one important Mali supplier in iron. The Sourou River that connects the Inland Niger Delta to the Mouhoun River was very likely a thriving trade highway. There is impressive evidence of iron metallurgy all over the study area. It consists of iron ore mines, some with complex systems of connected galleries and tunnels, open-air mines and quarries, smelting sites with large amounts of slag, furnace installations, and habitation sites, with varying quantities of iron artifacts (Holl 2014).
A number of sites distributed all over the Mouhoun Bend landscape were mapped and tested (Holl 2009b, 2014; Holl and Kote 2000). Late Stone Age scatters of lithic artifacts were recorded on the Mouhoun River shore, and four mound clusters were tested. They range in chronology from c. 760–210 bce to 1410–1650 ce at Tora Sira Tomo, c. 350 bce–120 ce to 1290–1450 ce at Kerebe Sira Tomo, and c. 440–750 to 980–1260 ce at Diekono.
Tora Sira Tomo (TST) mound complex is the largest of the settlement complexes found in the study area, with seventeen distinct mounds spread over 900 m west-east and 500 m north-south. TST-3, the largest single mound, is stretched along its northern edge and measures 260 m in length west-east, and 120 m in maximum width north-south. All seventeen mounds were tested. Five, TST-1, TST-2, TST-4, TST-9 [Ring Site], and TST-17. are special-purpose sites. The first is an iron-smelting workshop; the second a laterite quarry for both iron ore and construction material extraction; the third a cloth processing and dyeing site; the fourth a special burial site; and the fifth a shea-butter oil-production workshop. The remaining twelve mounds appear to have been standard habitation mounds with varying intensities and lengths of occupation.
Tora Sira Tomo (TST-1), the iron smelting workshop, is located at about 200 m southwest of the main mound (TST-3). It is sub-circular in shape, measures 18 m in length, 15 m in width. and 1.30 m in maximum height. The total of the excavated sample amounts to 65 m2 and covers the whole range of archaeological remains associated with iron-smelting. A large number of clay vessels set in upside-down positions were found disposed along the northern part of the iron-smelting complex (figure 15).
The furnace probe is located at the center of the site and cuts through the thickest portion of the archaeological deposit. It measures 40 m2 and consists of a 7 × 2 m trench oriented NW-SE abutting a larger SW-NE 7.5 × 4 m excavation unit. The probe’s stratigraphic sequence measures 1.50 m in maximum thickness and is made of four layers:
Layer 4 (0.00–0.60 m): brown-gray silty clay topsoil, partly termite mound;
Layer 3 (0.60–0.80/0.90 m): light brown-gray sediment from the collapsed furnace, including slag, blowpipes, and furnace brick fragments;
Layer 2 (0.80/0.90–1.30 m): brown-yellow hard and compact clay; and
Layer 1 (1.30–1.50 m): light brown-gray sediment with laterite gravels.
The base of a relatively large iron-smelting furnace was found at 0.45 m below the surface (figure 16). A line of red bricks found along the trench section suggests the uncovered furnace chimney to have measured at least 3 m in height. A fire-hardened surface was exposed on the eastern side of the furnace, the mouth of which was oriented northeast. The exposed furnace base measures 1.80 m in diameter. Its wall, 0.20-m thick, built with superimposed irregularly shaped clay lumps in two layers, an inner and an outer one, was preserved up to a height of 0.25 m. A group of broken and complete tuyères was exposed on the north flank of the furnace, with a set of three clay vessels on the fire-hardened surface on the east flank.
Slag, brick fragments, and broken tuyères filled the inner part of the furnace. This deposit was accumulated atop a tuyères level at 0.60 m below the surface, above a relatively thin bottom slag. These eight relatively well-preserved tuyères converge to the center of the furnace, within the middle of which is a mass of burnt clay, bricks, and slag, capped with a whitish 5- to 10-cm thick circular chalky deposit (figure 17). The preserved segments of the eight tuyères are more or less paired. They measure 30 cm to 40 cm in length and 10 cm in diameter at the proximal end and 5–6 cm at the distal one. The more or less balanced arrangement of the tuyères, coupled with the northeastern orientation of the furnace mouth, suggest that this installation was a natural draft one.
The circular white chalky deposit at the center of the furnace is presumably made of the remains of the fluxing material used in the smelting process. It is not yet known if this was an intentional addition to the furnace or the result of the kind of wood used as fuel (Haaland and Shinnie 1985; Schmidt 1996). In any case, fluxing material optimizes the use of fuel by lowering the temperature at which the iron ore starts to melt. Surprisingly, the bottom slag is relatively small in size, and the structure of the furnace surprisingly appears much more complex and interesting than thought initially. The remaining portion of the furnace was still to be found 1.20 m below the surface (figure 18), 0.60 m below the level of horizontally laid tuyères. A tronconic-shaped underground chamber was dug in the natural brown-gray silty clay deposit. It measures 0.60 m in diameter at bottom, with the base and wall lined with a mixture of crushed laterite gravel and clay. Fourteen vertical but slightly tilted tuyères arranged into two distinct sets were found in this part of the furnace installation. The western set has six tuyères, and the eastern one eight (figure 18), with the central space filled with termite nest material. The tuyères found at the bottom of the furnace had no direct connection with the combustion chamber. The six specimens from the western set measure 26 to 14 cm in length and 10 to 13 cm in maximum diameter. The eight ones from the eastern set are longer on the average, 26 to 40 cm, with a narrow diameter range of 11–12 cm. These tuyères were not used in any smelting process yet, and were filled with sediment that was easily removed. This suggests that the iron-smelters had designed a system allowing for the production of ready-to-use blowpipes, clearly an important economy of scale. A new supply of dry tuyères was set to be fired below the combustion chamber, taking advantage of the high temperatures generated by the furnace during the iron ore smelting process. Once the process was completed, the furnace was left to cool, the bloom was collected, and the new load of fired tuyères was recovered to run the next shift.
TST-1 furnace structure is a relatively sophisticated piece of craft engineering. There is no known case in African literature on metallurgy, in archaeology, as well as in ethnography (Bisson et al 2000; Coulibaly 2006; Kiethega 2006). The furnace was a natural draft one, operating without bellow blowers on the natural strength and persistence of the dry season northeastern wind (the Harmattan).
However, the greatest surprise of the TST-1 smelting site excavation was the radiocarbon date obtained from a large charcoal sample collected on the fire-hardened surface at less than one meter from the furnace mouth. The reading shows the smelting site to date to (ISGS 4349, 2360 ± 70 bp) 501–386 bc (1 sigma) or 761–212 bc (2 sigma). It is clearly an early case of an iron-smelting furnace in this part of West Africa, west of Niger-Nigeria where earlier iron-smelting sites were already recorded (Grebenart 1985, 1988; Okafor 1993, 2002; Holl 1997, 2009c; Holl and Kote 2000). The technical expertise involved in the conception, construction, and operation of the TST-1 furnace is very impressive indeed.
The site is divided in two parts, with the furnace in the middle axis. The sets of complete or near complete vessels were found exclusively in the north half and iron ore smelting by-products were discarded in the south half. This site layout can be explained by the intermittent, very likely seasonal use of the smelting site. At the peak of the production season, the natural draft furnace can be in operation for days. Working crews take shifts in order to keep the momentum and as such may have camped nearby in lightly built shelters. The recorded pottery is predominantly made of relatively large liquid containers that provided the working crews with necessary beverages. The variation in decoration patterns can have many probable explanations: On the one hand, working crew members may have been recruited from different surrounding settlements, with some serviced by different potters. They bring with them the material they use in their respective villages. In that case, the recorded diversity reflects the elasticity of the actual pottery offer. On the other hand, the smelting site may have been in use for a relatively long period that may have witnessed some variation in the patterns of pottery decoration. A varying combination of both suggestions is also a genuine possibility.
The data recorded in this part of the Mouhoun Bend add a significant novelty to the debate of the development of African metallurgies. The iron-smelting furnace from TST-1 points very directly to a local case of technological innovation that took place in the middle of the first millennium bce c. 700–200 bce. The local expert smelters designed a dual-purpose furnace that produced important economies of scale. On windy days of the West African dry seasons, the Harmattan—northeasterly—can blow for days without interruption. Natural draft furnaces were designed to take advantage of this wind power and to be operated shift after shift without significant interruption except for the removal of the bloom and the retrieval of a new batch of ready-to-use blowpipes. After several episodes of exposures to high temperatures, the tuyères, essential components of the venting system, can crack and break and be clogged by liquid slag. They could be replaced without the need to halt the ongoing smelting operation. This stunning innovation took place during the middle of the first millennium bce and supports the previous findings from nearby Bena, at 12o 04’ 05” N/4o 11’ 02” W in Western Burkina Faso, dated to c. 360–220 bce (Kiethega 2006; Coulibaly 2006).
African Origins of Iron Metallurgy!
African metal working traditions are remarkably diverse. There are, in fact, three distinct situations: A mobile herder copper-producing tradition emerged in the Akjoujt region of today’s Mauritania, probably in the second millennium bce, and lasted up to 4–300 bce. Pastoral-nomadic copper and iron-working traditions developed in the Termit-Air-Eghazzer area of Niger. And finally, iron-producing traditions developed in the rest of the continent, from the Middle Senegal Valley in the west to the eastern end of the Adamawa plateau in the center, and the Great Lakes regions in the East, ranging in date from the late third millennium to 6–500 bce.
Copper was exploited and used for the manufacture of prestige artifacts, elements of personal adornment and weapons in the Eghazzer basin and the Termit massif in Niger Republic and the Akjoujt region in Mauritania. Iron played a similar role elsewhere in the continent, initially providing weapons and status objects and later a broad range of tools. The chronology of the emergence of metallurgical practices has changed considerably during the past two decades, thanks to the multiplication of research projects and radiocarbon dates. The earliest instances of iron metallurgy dated to the late third–second millennium bce are found along the northern margins of the equatorial forest in what was very likely a shifting forest-savanna ecotone. It is the case at Lejja in the Nsukka region in Nigeria in the west, Oboui in the Bouar region in Central Africa in the eastern confine of the Adamawa plateau, and Gbatoro near Djohong in Cameroon (Zangato and Holl 2010). Radiocarbon dating deserved to be complemented by other techniques like thermoluminescence testing of furnace walls to shift the research agenda to more interesting social issues. Habitation sites and burial grounds associated with metal-producing localities, if studied carefully, can open access to the evaluation of patterns of consumption and use of metal artifacts. This will allow for a more balanced understanding of the past role of metals and a better grasp of past technological change.
Fieldwork upon which part of the paper is based was funded by the Centre National de la Recherche Scientifique (CNRS), France; National Geographic Society Grant #6378-98, and the University of California, San Diego start-up funds. The Centre National de Recherche Scientifique et Technique (CNRST) of Burkina Faso Republic provided research permits. I am grateful to Lassina Kote for his help in the field and the opportunity to conduct an exciting archaeological research project in the Mouhoun Bend.
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