Ranking of Cape Geophytes by Proxies for the Benefits and Costs of Harvesting their Underground Storage Organs

Abstract The Cape Floristic Region (CFR) has the world’s highest diversity of plants with underground storage organs (USOs). This rich USO flora has been proposed as a key food source for modern humans in the Late Pleistocene. For 130 Cape geophyte species, we quantified proxies for energetic benefits (USO size and nutrient content) and harvesting costs (USO depth and anti‑nutrients), then ranked species by their likely attractiveness to foragers. We identified six USO types. Small and large corms (53.8% of species) offer the highest energy returns with only moderate harvesting and processing costs. Bulbs (15.4%) are easy to dig, require little preparation, and provide moderate energy. Small and large rhizomes (12.3%) offer modest energy and, especially when large, tend to be fibrous and tannin‑rich. Tubers (18.5%) are low in energy but may have been valued as thirst quenchers. Archaeological and ethnographic evidence from Cape hunter‑gatherers aligns with these rankings.