The resilience to human foraging of intertidal resources on the south Cape coast of South Africa and the implications for pre-historic foragers

The extent to which modern humans relied upon intertidal resources, and the impact that this food source had on their cognitive and social development, remains contentious. An outstanding question is whether such a resource could have provided a sufficiently reliable and essentially continuous supply of resources to support communities during the Middle Stone Age (MSA). The south Cape coast of South Africa contains abundant evidence dating back to 164 000 years ago (ka) to show that the intertidal zone of this area was highly productive and was intensively used by MSA humans. In this paper we present the results of an experimental approach to answering the question of whether resources could have been sufficiently resilient to support communities similar in size to those of the Middle Stone Age. For a period of 10 months, we monitored the depletion of shellfish in the two dominant types of marine habitat (aeolianite and Table Mountain Sandstone) that occur on the south Cape coast, following intensive harvesting by indigenous foragers every two weeks or every four weeks. We found no evidence of lasting depletion in either type of habitat at either foraging frequency. We also found that replenishment of the foraged areas soon occurred (within two weeks) by repopulation from deeper water rather than by a long-shore movement. The most important prey species in this process was the highly mobile gastropod mollusk Turbo sarmaticus, which made up 81.9% of calorific harvest. Overall, mobile species made up 92.2% of the calorific harvest. Another factor that contributed to the resilience of the system is the nature of the coastline of the south Cape. This is characterised by extended shallow bathymetries of hard substrata that provide “pantries” of mobile invertebrates for restocking depleted intertidal habitats. We argue that the presence of such a reliable, easily procured, and nutritionally beneficial source of food may have played an important role in the development of more complex types of social behaviour than previously existed.