Archaeology of Zilum

Prior to the early 2000s, geophysical methods for mapping subsurface structures and archaeological features were virtually non-existent in the archaeological work of sub-Saharan Africa. Tite (1966) and Fagg (1969) were the first to attempt to use magnetometry in sub-Saharan Africa as they studied Taruga, a Nok Culture site in Nigeria.[2] Although the findings from this early use of magnetometry were less precise than they would be today, their work demonstrated the importance and efficacy of magnetometry in a sub-Saharan context. Carlos Magnavita furthers this work by employing magnetic survey at Zilum in northeastern Nigeria, demonstrating how geophysical methods are advantageous, despite additional costs, for archaeological work south of the Sahara as they provide data not accessible via traditional survey and excavation methods.[2] The significance of geophysical methods in sub-Saharan archaeological work is illustrated by Magnavita as

The evidence revealed by the magnetic survey in Zilum is significant for field research on sub-Saharan African archaeological sites, as it shows that only the use of traditional investigation methods can passively handicap the understanding of the nature of past settlements.[2]

Cutting overview ditch

Magnavita's magnetic survey was carried out in the eastern and southern parts of the site using a Fluxgate-Magnetometer FEREX 4.032.[2] The significant distribution of pits at this site were discovered by magnetometry due to the potsherds discarded and/or used in these pits. Some pits were visible or identifiable from the surface due to the abundance of cultural material at the surface (oftentimes broken pottery), but magnetometry allowed for the exact mapping of these pits. This is because fired clay materials generate a magnetic disturbance that contrasts with the surrounding ground material, essentially illuminating the shape of man-made features. Many of these pits were dug for the extraction of clay for craft production, but they were then used for borrowing, refuse, and storage.[2]

The presence of a ditch-and-rampart system suggests that Gajiganna Phase III was less peaceful than the previous phases as the earlier settlements do not show evidence of fortification.[1] The presence of numerous storage pits indicates the recurrence of and reliance on food security, as well as supports the construction of buildings/structures created from the material dug out of these pits, like huts and rampart walls. Interpretations of culture and lifestyle would not have been possible without the use of magnetometry as the largest number of pits, trenches, and ditches would have remained undetected.[2]

Zilum cutting southern ditch section

Archaeological and paleoethnobotanical evidence suggests that the inhabitants of Zilum relied more heavily on the cultivation of edible plants, like pearl millet and cowpeas, than on the consumption of meat.[2] The large amount of storage pits aids in this interpretation, as does a marked decline in the amount of animal remains recovered from Zilum's settlement deposits as compared to other Gajiganna sites of previous phases in the region. Other communities within the Gajiganna culture had economies based heavily on the husbandry of animals like cattle, sheep, and goat. The foraging of wild plants and fishing also played roles in communities of this culture.[2]

The economy of Zilum did not rely exclusively on the production of food. Through the mapping of finds, two distinct concentrations of artifacts were found that can be related to craft activity. The first was found in the southern part of the site and is consisted of tools for pottery production, particularly ceramic tampers. The second was found in the eastern section of the site and consists of grooved stones, suggested to be related to the production of stone beads or bone points.[1]

Zilum cutting refuse pit

In the central region of the surveyed site, a concentration of archaeological features was find, likely relating to craft activity. A series of pits in varying sizes were discovered to have been lined with a layer of clay. Chemical analysis of this layer showed a notably high concentration of elementary sulphur and dimethyltrisulfid, neither of which occur naturally in clay and are thus thought to be associated with human activity. These pits are likely related to the tanning of skins as the arrangement of pits can be compared to modern facilities in West Africa where sodium sulphate is used as a tawing agent, which may account for the high concentrations in the clay lining.[1]

This craft-related evidence, paired with the ceramic findings discussed here later, led archaeologists to conclude that artisans inhabited Zilum and likely produced a large portion of the material culture for the larger community. This conclusion is furthered by the high population density (1,750-2,500 people on the 12-hectare settlement) as it is unlikely that each household would possess the skill required to create their own pottery, especially in regard to large storage vessels.[2][1]

Contemporary sites in the immediate and farther vicinity of Zilum have been discovered and surveyed. As of 2006, fourteen distinct settlements have all been dated using pottery analogy to be potentially contemporaneous with Zilum. These settlements vary in size with the largest, Galgalkura A, likely to have been at least the size of Zilum itself. It is thought that the size differences point to site-size hierarchy, which is unseen in previous Gajiganna phases. This site-size hierarchy becomes apparent near Zilum as it is encircled by sites between 2.5 and 4.0 km of smaller size, with Zilum seeming to have been above these settlement groups. According to Carlos Magnavita, it is very probable that Zilum consisted of a fortified and nucleated settlement that, assuming the contemporaneity of the neighboring sites, likely oversaw a size-based hierarchy in the mid-first millennium BCE.[1]