Isotopic and microbotanical insights into Iron Age agricultural reliance in the Central African rainforest

Abstract

The emergence of agriculture in Central Africa has previously been associated with the migration of Bantu-speaking populations during an anthropogenic or climate-driven ‘opening’ of the rainforest. However, such models are based on assumptions of environmental requirements of key crops (e.g. Pennisetum glaucum) and direct insights into human dietary reliance remain absent. Here, we utilise stable isotope analysis (δ13C, δ15N, δ18O) of human and animal remains and charred food remains, as well as plant microparticles from dental calculus, to assess the importance of incoming crops in the Congo Basin. Our data, spanning the early Iron Age to recent history, reveals variation in the adoption of cereals, with a persistent focus on forest and freshwater resources in some areas. These data provide new dietary evidence and document the longevity of mosaic subsistence strategies in the region.

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

“…That pearl millet may have been put to special use, is also indirectly suggested by a study on stable isotopes in human and animal bone collagen and tooth enamel from four Central African Iron Age rainforest sites, including Bolondo and Imbonga (Bleasdale et al 2020). Bone collagen samples from LIA Bolondo humans show δ 13 C values between − 21.0 and − 16.3‰, consistently higher than those of the wild fauna and fishes from the same site; this points to a mainly C 3 -based human diet with some C 4 component, possibly pearl millet.…”

“…Faunal and human bone as well as food remains have recently been subjected to stable isotope analyses allowing for dietary Calibrations were calculated with CalPal v. 2020.8 (Weninger and Jöris 2008) using the IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (Reimer et al 2020). Southern Hemisphere Correction was not applied in view of all sites' very close proximity to the equator Semi-quantitative values: x = < 0.1 g/l, xx = 0.1-1.0 g/l, xxx = >1.0 g/l and ecological inferences (Bleasdale et al 2020). Founded around the mid-14th century ad (Poz-93614; Table 1) during the LIA Wema Phase, Bolondo has featured repeatedly raised house platforms from the beginning; these have fused over time to form an artificial island.…”

“…Stable isotope studies by Amy Styring (Bleasdale et al 2020) on seven charred potential food fragments from Bolondo have revealed a signature of C 3 plants or aquatic resources in five cases (δ 13 C between − 27‰ and − 24‰) and a C 4 -signature (δ 13 C around − 9‰) in two cases. These values are in line with the origin of the food remains from different sources, including C. americanus and tubers, possibly Dioscorea spp.…”

“…The finds of charred parenchyma point to the first method. Potential evidence for cooking of the tubers in pots is provided by the charred food remains with amorphous structure, and the isotopic C 3 signature of some food remains from Bolondo (Bleasdale et al 2020).…”

Gathering and Sowing Across the Central Maya Lowlands: A Review of Plant Use by Preceramic Peoples and the Early to Middle Preclassic Maya

“…This model's legacy has had a longstanding effect on how other places around the world were understood to have transitioned to food production (Langlie et al 2014). Food production in the Americas (but also further afield; see, for example, Bleasdale et al 2020;Castillo et al 2018) took different pathways and therefore proves a challenge to Old World models. The first major point is that there were no large animals to domesticate in Mesoamerica.…”