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

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.

Analysis of Early Iron Age (2500 BP) and modern period (150 BP) starch grains in Western Central Africa

“…Macrobotanical remains of several taxa identified in this study have been reported in southern Cameroon and neighboring regions for the EIA, for example the Gabon nut, pearl millet, the raffia palm, cowpea, and the Bambara nut 1 , 3 , 5 , 6 .…”

“…The reports of Musa phytoliths in 1 st millennium BC contexts from the Yaoundé region 2 have been debated 11 . More recently, this taxon has been reported from the Inner Congo Basin, but only for Late Iron Age contexts 3 .…”

“…For example, was pearl millet cultivated continuously since the EIA? Evidence of carbonized remains of this plant suggest that it was grown in the Inner Congo Basin also between the fourteenth and sixteenth centuries AD 3 , but it remains to be seen if this can be applied to our study region. Moreover, when does another cereal, sorghum ( Sorghum bicolor ), appear in the WCA?…”

“…The plant-based diet of ancient African populations has been a longstanding debate over the past 20 years 1 – 3 . To date, data obtained from archaeobotanical, isotope, and more recently organic residue analyses have provided significant information on the topic of plant-related subsistence practices in WCA during the Early Iron Age (EIA).…”

“…The analysis of macrobotanical remains (seeds and other plant parts visible to the naked eye) has shown that this period coincides with the introduction of a West African package consisting of a cereal, pearl millet ( Pennisetum glaucum syn. Cenchrus americanus ), and a legume, cowpea ( Vigna unguiculata ) 3 , 4 . At the same time, these early agricultural communities relied on other resources that include fruit trees and palms (notably Canarium schweinfurthii and Elaeis guineensis ) and most likely tubers (i.e., Dioscorea ssp.)…”