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Singels E, Potts AJ, Esler KJ, Cowling RM, Marean CW, De Vynck JC.2015. Foraging potential of underground storage organ plants in the southern Cape, South Africa. PeerJ PrePrints3:e1573v1https://doi.org/10.7287/peerj.preprints.1573v1
Underground storage organs (USOs) serve as a staple source of carbohydrates for many hunter-gatherer societies and they feature prominently in discussions of diets of early modern humans. While the way of life of hunter-gatherers in South Africa’s Cape is no longer in existence, there is extensive ethnographic, historical and archaeological evidence of hunter-gatherers’ use of such plants as foodstuffs. This is to be expected, given that the Cape supports the largest concentration of plants with USOs globally. The southern Cape is the location of several Middle Stone Age sites that are highly significant to research on the origins of behaviourally modern humans, and this provided the context for our research. Here we evaluate the foraging potential of USOs by identifying how abundant edible biomass is in a coastal setting of the southern Cape, how easily it is gathered, and how nutritious it is. We staged a range of foraging events to provide an indication of the potential return rates for selected USOs when a forager is likely to be naïve about foraging for them. Nearly all of the sites sampled (83%) contained edible USOs, and the edible biomass can be highly concentrated in space. The edible USO biomass fell within the range of biomass observed in areas supporting extant hunter-gatherer communities. The six USO species we assessed for nutritional content contained between 40-228 calories/100 g. They also grow near the soil surface, mostly in sandy soils, and were gathered with minimal effort. Some 50% of the foraging events conducted yielded enough calories to meet the daily requirements of a hunter-gatherer of small stature within 2 hours. Thus, we demonstrate that USOs are a readily available source of carbohydrates in the southern Cape landscape and that they likely played a critical role in providing food for early humans.
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Appendix A, B & C
Appendix A: The different vegetation types and USO types in the southern Cape Appendix B: The species list of underground storage organs found in the 100 plots, sampling the vegetation of the southern Cape. Appendix C: USO foraging return rates