Iron Age human subsistence, environment, and climate in the Inner Congo Basin (Democratic Republic of the Congo)
Final Report Abstract
For the last 2400 years, sedentary societies have been living in the rainforests at the heart of Central Africa – on what, and under which environmental conditions? These were the major research questions asked by the present project. Around AD 1880, much like today, local populations relied on plantain, manioc, maize, sugar cane and wild fruits. Fishing and hunting considerably supplemented their diet, while domestic goats and poultry contributed little. Until now, nothing was known about the staple foods of the Iron Age ancestors of these people. Manioc and maize can be ruled out because both originated in the Americas and only made their way into the heart of Africa towards the end of the Early Modern Period. Neither were bananas native to Africa, and both inception and course of their use history on that continent remain largely obscure. The African tuber plant yams is an obvious candidate, but is difficult to prove and has not so far been empirically attested anywhere. The beginnings of domestic animal husbandry in Central Africa are also unresolved. From 2015 to 2017, excavations of Early (c. 400 BC – AD 100) and Late Iron Age settlement sites (c. AD 1300–1650) with archaeobotanical and archaeozoological sampling as well as pollen coring were undertaken in the equatorial region of Democratic Congo. The first rainforest settlers, around 400 BC, were pottery-making immigrants. Whence they had come remains unclear, but the project results show that they not only had hitherto unknown neighbours, but from the very beginning practised iron metallurgy and food production, including pearl millet and cowpea. Pearl millet is considered a savanna plant that requires a distinct dry season to mature. However, a cultivation experiment within the project proved that pearl millet can also be cultivated in year-round humid equatorial rainforest climate. Surprisingly, evidence of its cultivation was found until around AD 1600. Since no site yielded more than a few pearl millet grains, some of them showing morphological modifications, this cereal may have been used for beer production rather than as a main food. Other staple food plants used were the widespread oil palm and probably yams, the latter attested by charred parenchyma remains. According to our findings, banana cultivation goes back to at least to around AD 1400, and newly found bones of domestic goat likewise testify to its pre-colonial presence since AD 1450 at the latest. Prospections in tropical peatlands yielded cores with good pollen preservation. They go back as far as 38,000 years and allow long-term reconstructions of vegetation history and, for the first time in the Inner Congo Basin, empirically testing of the refugia theory according to which tropical rainforests went through climate-controlled phases of strong contraction and expansion. Further onsite and nearsite pollen profiles were drilled in connection with archaeologically investigated Iron Age settlement sites. These promise to provide additional information about human contributions to vegetation change over the last two and a half millennia. Enhanced chronological control is ensured by 118 new radiocarbon dates that more than doubles the stock available so far.
Publications
- (2016). Archaeology in the Equatorial Rainforest of Africa. University of Cologne, Faculty of Arts and Humanities, Research 2016/17: 36–37
Wotzka, Hans-Peter
- (2019), Ecology and culture of millets in African rainforests. Ancient, historical, and present-day evidence. In Eichhorn, Barbara & Alexa Höhn (eds.), Trees, grasses and crops. People and plants in sub-Saharan Africa and beyond. Frankfurter Archäologische Schriften 37 (Bonn: Rudolf Habelt) 407–429
Wotzka, Hans-Peter
- (2019), Experimenteller Anbau von Perlhirse (Pennisetum glaucum) im äquatorialen Regenwald des Inneren Kongobeckens, August–November 2016. In: Meurers-Balke, Jutta, Tanja Zerl & Renate Gerlach (eds.), Auf dem Holzweg … Eine Würdigung für Ursula Tegtmeier. Archäologische Berichte 30 (Heidelberg: Propylaeum) 269–284
Wotzka, Hans-Peter
- (2019), On the ‘search for beer’ in the archaeobotanical records of West and Central Africa – a methodological contribution. In: Eichhorn, Barbara & Alexa Höhn (eds.), Trees, grasses and crops. People and plants in sub-Saharan Africa and beyond. Frankfurter Archäologische Schriften 37 (Bonn: Rudolf Habelt) 109–118
Eichhorn, Barbara
- (2020), Isotopic and microbotanical insights into Iron Age agricultural reliance in the Central African rainforest. Communications Biology
Bleasdale, Madeleine, Hans-Peter Wotzka, Barbara Eichhorn et al.
(See online at https://doi.org/10.1038/s42003-020-01324-2)
