The south coast of South Africa provides the earliest evidence for Middle Stone Age (MSA) coastal resource exploitation by early Homo sapiens. In coastal archaeology worldwide, there has been a debate over the general productivity of intertidal foraging, leading to studies that directly measure productivity in some regions, but there have been no such studies in South Africa. Here we present energetic return rate estimates for intertidal foraging along the southern coast of South Africa from Blombos Cave to Pinnacle Point. Foraging experiments were conducted with Khoi-San descendants of the region, and hourly caloric return rates for experienced foragers were measured on 41 days near low tide and through three seasons over two study years. On-site return rates varied as a function of sex, tidal level, marine habitat type and weather conditions. The overall energetic return rate from the entire sample (1492 kcal h(-1)) equals or exceeds intertidal returns reported from other hunter-gatherer studies, as well as measured return rates for activities as diverse as hunting mammals and plant collecting. Returns are projected to be exceptionally high (∼ 3400 kcal h(-1) for men, ∼ 1900 kcal h(-1) for women) under the best combination of conditions. However, because of the monthly tidal cycle, high return foraging is only possible for about 10 days per month and for only 2-3 h on those days. These experiments suggest that while intertidal resources are attractive, women and children could not have subsisted independently, nor met all their protein-lipid needs from marine resources alone, and would have required substantial additional energy and nutrients from plant gathering and/or from males contributing game.

Even a simple human foraging system has a large number of moving parts. Foragers require a complex decision making process to effectively exploit the spatially and temporally variable resources in an environment. Here we present an agent-based modelling framework, based in optimal foraging theory, for agent foragers to make mobility and foraging decisions by weighing expected caloric returns against geographic and social factors, and forecasted future return rates. We apply our Paleoscape model to a spatially explicit South African coastal landscape to better understand the human foraging system of the Middle Stone Age, when foragers began systematically exploiting a wide variety of flora and fauna in both terrestrial and inter-tidal environments. We also discuss the broader importance of agent-based models of foraging systems for a wide variety of archaeological research questions.

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