Dietary practices in Iron Age Northern and Central Botswana: microbotanical evidence from dental calculus

Abstract The tempo of crop adoption in the Kalahari Basin Area remains imperfectly understood, with most inferences drawn from sparse macrobotanical finds and stable isotope baselines rather than direct evidence of plant use at the individual level. A long-standing question — the ‘Kalahari Debate’ — concerns whether forager communities in southern Africa were isolated from, or progressively integrated with, neighbouring food-producing societies. The more recent three-layer approach suggests a drawn-out process of complex Holocene interactions among Wilton-producing foragers, Late Stone Age Khoe-Kwadi sheep herders, and later Bantu farmers. This study assesses whether cereals became dietary staples in northern and central Botswana during the early part of the Late Iron Age. We analysed microbotanical remains in dental calculus from four individuals from Nǃoma, Taukome and Xaro. Short-cell phytolith morphotypes consistent with Panicoideae were common at Nǃoma and Taukome, with rare dendritic long-cells suggestive of husk tissue; while starches were scarce. Xaro produced very low counts dominated by Pooideae short-cells. Proteomic analysis of the three dental calculus samples yielded no dietary proteins but did identify oral bacteria, including those associated with periodontal disease. Dietary findings align with published stable carbon isotope evidence: Nǃoma and Taukome show values consistent with diets rich in C 4 crops (for example sorghum and pearl millet). At Nǃoma, differences between childhood tooth enamel (records childhood diet) and adult bone collagen (records primarily adult diet) point to a shift from C 3 foraging/fishing in youth to C 4 crop consumption in adulthood. These results provide the first direct microbotanical evidence of cereal consumption in Iron Age Botswana, consistent with the KBA framework in which crops became embedded through sustained forager, herder, and farmer interaction.