Iron Age plant subsistence in the Inner Congo Basin (DR Congo)

Vegetation History and Archaeobotany https://doi.org/10.1007/s00334-021-00865-8 ORIGINAL ARTICLE Iron Age plant subsistence in the Inner Congo Basin (DR Congo) Katharina Neumann1 · Barbara Eichhorn1 · Hans‑Peter Wotzka2 Received: 21 October 2020 / Accepted: 12 November 2021 © The Author(s) 2022 Abstract Around 400 bc, pottery- and iron-producing populations immigrated into the Inner Congo Basin (ICB) and subsequently spread upstream some major tributaries of the Congo River. Until recently, their subsistence was almost completely unknown. We present an archaeobotanical study of three sites in the ICB covering parts of the Early Iron Age (ca. 400 bc-ad 650) and of the Late Iron Age (LIA) as well as subrecent times (ca. ad 1300–2000). We studied 82 flotated samples of botanical macroremains, and 68 soil phytolith samples, recovered from the terra firme sites Iyonda and Mbandaka, and the floodplain fishing camp site of Bolondo. The EIA assemblage from Iyonda yielded domesticated Cenchrus americanus (pearl millet), Vigna unguiculata (cowpea), Canarium schweinfurthii, Elaeis guineensis (oil palm), several wild plants, and parenchyma fragments tentatively attributed to Dioscorea sp. (yams). The exploitation of these plants originated in the savannas and forest-savanna ecotones of West Africa. The presence of C. americanus in LIA contexts at Bolondo and Mbandaka, dated to ca. ad 1350–1550, indicates that its cultivation is not dependent on a seasonal climate with a distinct dry season, contrary to previous views. The role of C. americanus as a staple is difficult to assess; it might have been used for special purposes, e.g. beer brewing. In spite of extensive screening, we did not detect any banana phytoliths in the EIA samples. Musa phytoliths were only present in LIA contexts after ca. ad 1400, leaving room for the possibility that the introduction and spread of Musa spp. AAB ‘Plantain’ in the ICB was a late phenomenon. Keywords Archaeobotany · Central African rainforest · Human nutrition · Musa · Cenchrus americanus · Vigna unguiculata · Bantu expansion Introduction In comparison with other rainforests of the world, the Holocene prehistory of the Central African rainforest is still largely unknown. Some regions of the Central African rainforest have seen more intensive archaeological research, such as Cameroon, Gabon or the Central African Republic (Van Noten 1982; Clist 1989, 1995, 2005; Lanfranchi and Communicated by F. Bittmann. Barbara Eichhorn—deceased. * Katharina Neumann 1 Institute for Archaeological Sciences, Goethe University, Norbert‑Wollheim‑Platz 1, 60629 Frankfurt am Main, Germany 2 Present Address: Institute for Prehistory, African Archaeology, Cologne University, Jennerstraße 8, 50823 Köln, Germany Clist 1991; Essomba 1992; Oslisly 1993; Mbida Mindzie 1995/1996; Zangato 1999, 2000, 2007; Assoko Ndong 2002; Marliac 2006; Lavachery et al. 2010; Gouem Gouem 2011; de Saulieu et al. 2015; Eggert and Seidensticker 2016; Lupo et al. 2018). But the Inner Congo Basin (ICB) in the Democratic Republic of the Congo (DR Congo), covered by dense evergreen rainforest and swamp forest, counts among the most severely under-researched areas, not only within Central Africa but also in sub-Saharan Africa at large. This stands in marked contrast to the significance of the region for one of the most challenging topics of African culture history, the Bantu expansion (Nurse and Philippson 2003; Eggert 2005, 2012; de Maret 2013; Bostoen et al. 2015). Earlier archaeological work in the ICB has revealed that probably Bantu speaking pottery- and iron-producing populations immigrated into the area in the second half of the first millennium bc (Eggert 1993; Wotzka 1995; Livingstone Smith et al. 2017) and subsequently spread upstream along some major tributaries of the Congo River. However, until recently, nothing was known about the subsistence of these 13 Vol.:(0123456789) Vegetation History and Archaeobotany immigrants. Were they farmers, i.e. did they mainly rely on domesticated plants and animals, as suggested by earlier, mainly linguistic-based studies (Vansina 1990; Phillipson 2002; Diamond and Bellwood 2003; Bostoen et al. 2013, 2015; Russell et al. 2014)? And to what extent did wild resources, likewise suggested as important by linguistic evidence (e.g. Bostoen et al. 2013; Bostoen 2014; Bostoen and Koni Muluwa 2017), contribute to their economies? Similar questions concern the further development of Iron Age human subsistence and nutrition in the ICB. The earliest available historical source on staple foods in the area only dates back to the eve of European colonisation. We owe it to Curt von François (1888) who observed, in 1885, ubiquitous plantain (Musa spp. AAB ‘Plantain’) cultivation, supplemented only here and there by Manihot esculenta (manioc), Zea mays (maize) and Saccharum officinarum (sugar cane). From his detailed descriptions, it is clear that Elaeis guineensis (oil palm) and fish were likewise important, while domestic animals, hunting, and gathering were secondary. Of the staple foods consumed at the time none is indigenous to the Congo Basin, nor indeed to Africa. Also it is well attested that the New World crops M. esculenta and Z. mays, although principally available on the continent from around ad 1500, never gained importance in large parts of the ICB before the early 20th century (R Eggert 1987). When and how did plantains make their appearance, and what did equatorial rainforest economies look like before the introduction of M. esculenta and Z. mays? Above all, what did people principally eat before the late 19th century? So far, the evidence available on this question has been limited to piecemeal reports on a few individual finds of charred endocarps of oil palm or Canarium schweinfurthii (incense tree, Burseraceae) (e.g. MKH Eggert 1987; Wotzka 1995) and archaeozoological analysis of the very few terrestrial animal and fish bones found (Van Neer 1990, 1991, 2000). The most accurate and meaningful evidence of ancient plant use comes from the remains of the plants themselves in archaeological sites. However, archaeobotanical studies focusing on plant exploitation in the Central African rainforest are still very rare. Besides charcoal and the endocarps of oil palm, ubiquitous in archaeological sites of the area (e.g. Oslisly and White 2007; Hubau et al. 2014, 2015; Kahlheber et al. 2014b; Morin-Rivat et al. 2016; Höhn and Neumann 2018), direct material evidence of other useful plants is scarce. It is therefore not surprising that each new archaeobotanical find, although not more than a needle in a haystack, entails far-reaching interpretations for the whole Central African rainforest. Especially relevant for the Bantu expansion are a handful of sites in southern Cameroon dating to the first millennium bc that yielded macro- and micro-remains of domesticated plants. The Musa phytoliths from Nkang (Mbida et al. 2000; Mbida Mindzie et al. 200 (...truncated)