Reply To: April 28th Science, Society, and Power

Nik Petek – Reflections on seminar and lecture with James Fairhead, 28-04-2014

I wish to reflect on Fairhead’s lecture on ‘Dark Earths of Africa’, which took place in the afternoon and how archaeology can be used to discerning past human occupation by looking at darker soils.
In the lecture, Prof Fairhead was talking about how some of the best soils for cultivation are dark humic soils which were anthropogenically created or modified to contain a higher amount of nutrients, intentionally and unintentionally, through general human occupation. These soils are then years later used for cultivation and are highly prized, so much that people steal it. Because these soils are created by human occupation, archaeologists will eventually be working with and within these soils, and many routes of investigation open up analysing these soils from an environmental archaeological perspective.

Looking for darker soils and sediments or just sediments different to their surrounding is nothing new in archaeology. In fact, sediments and soils different from their surrounding are prime indicators of human occupation and/or activity. We can start with small features, such as post holes, which leave a small circular imprint (seen in plan) in the layer they cut. Graves, ditches, and many other modifications of the land also leave an imprint within the layers they cut through containing darker sediment/soil. It is how archaeologists discern features. That is not to say that all human modifications of the land create „darker spots“ or that only human activity creates a more humic sediment, but in many cases that holds true.As a discipline, then, archaeology is well placed to identify past human landscape modifications.

Many methods can be used to study the African Dark Earths from an archaeological perspective. You can survey a large extent of an area containing dark earths, e.g. in Guinea, and from that determine the level of occupation and density at any one point in time (of course that also requires collecting other archaeological evidence from which we can discern relative time periods). You can combine taphonomic and phytolith study (like at Catalhöyük) to determine plant use and where and how these were used and their parts disposed of. There is also the possibility of using geoarchaeological methods to discern the formation and later use of dark soils by humans. You can also draw correlations between the dark soils and the plant species present around and on them, and see which were propagated by humans (but not necessarily) and/or see how the landscape was modified post-abandonment.

Many correlations can be drawn between these African Dark Earth and pastoralists’ abandoned bomas in East Africa, on which a reasonable amount of research has already been done. Pastoralists pen their livestock, which causes an accumulation of dung within that pen. After a couple of years that settlement is abandoned and slowly vegetation starts to take it over. However, only specific grasses are adapted enough to grow within the nitrogen-rich soils created from dung decomposition, and they stand out in the landscape as glades. These glades attract later on a number of browsers and increase the biodiversity of the landscape.
Both these glades and the African Dark Earth are anthropogenic, and they show, in the long run, how human intervention can help the environment prosper. Moreover, they contain data on human dwelling within the environment and how humans changed it through time.