Productivity and resilience of intertidal resources available to extant human foragers on South Africa’s cape south coast: behavioural implications for early Homo sapiens

Studies of pre-historic lifestyles can be limited by a lack of preserved material and sites and resource misinterpretation is augmented by the vagueness of pre-historic subsistence lifestyles. The present can inform the past and this study‟s ethnoarchaeological approach, through modern analogues, examines productivity, resilience and temporal and spatial size variation of intertidal invertebrates on the Cape‟s south coast. O‟Connell (1995) defined the mutualistic relationship between ethnography and archaeology thus: “Archaeology‟s ultimate aim is understanding past human behaviour by patterns in the form and distribution of objects made or modified by humans in the past and knowledge of human behaviour and its material consequences in the present. The first provides direct evidence of past behaviour; the second, a basis for interpreting that evidence”. Coastal archaeology, specifically the contribution of coastal resources to pre-historic subsistence, has gained increased global interest (Erlandson, 2001; Erlandson and Rick, 2008; Codding et al., 2014). Apart from the high representation of preserved shell in coastal archaeological sites, interest in intertidal resources has also been sparked by their economic value compared to terrestrial resource options. Intertidal resources offer low-risk protein acquisition whereas terrestrial protein can be dangerous to procure. However, in the past intertidal subsistence was thought to offer low caloric yields or unfavourable cost-to-benefit relationships until Meehan (1982) convincingly demonstrated the potential caloric „profit‟ possible from coastal foraging; the Anbarra women of northern Australia were contributing significantly to the overall caloric requirements of those people. In South Africa, two possible evolutionary behavioural hypotheses arose from the addition of intertidal resources to pre-historic diets. As background, it is important to note that the oldest global evidence for shellfish procurement [164 000 years ago (ka)] is found on the Cape‟s south coast (Jerardino and Marean, 2010) and the evidence is enriched by other sites from around 110 ka (Voight, 1973; Thackeray, 1988; Henshilwood et al., 2001; Langejans et al., 2012). Furthermore, this period coincides with the emergence of cognitively modern Homo sapiens as evidenced in xx the palaeoarchives from many sites in the region (d‟Errico et al., 2005; Marean et al., 2007; Wurz, 2008; Henshilwood et al., 2009; Watts, 2010; d‟Errico et al., 2012). These features have greatly enhanced the significance and importance of this area to understanding human evolution. The two hypotheses are centred around the effect that intertidal resources could have had on the emergence of our unique species. The addition of a nutritionally beneficial resource to cognitive development is seen by some (Broadhurst et al., 2002; Parkington, 2010) to have driven this cognitive evolution, where others suggest that resources which are both productive and dependable create pro-social proclivities that drive cognitive development (Whitaker and Byrd, 2014; Marean, 2014) and facilitate the migration of humans (Fa, 2008; Codding et al., 2014). Both hypotheses argue that resources on the Cape‟s coast must have been productive and had to be a frequent addition to diet to underpin brain development. The increased frequency of coastal resource procurement or coastal adaptation is therefore seen as an attribute of, or requisite for our species. This thesis attempts to shed light on the contribution of intertidal resources to prehistoric ‒ especially Middle Stone Age (MSA) – subsistence economy on the Cape‟s south coast and the possible effect thereof on human behavioural evolution. The first aim was to investigate the spatial productivity (once-off patch caloric profitability in numerous patches) of intertidal resources and the environmental and behavioural variables affecting it. The second aim was to investigate the resilience of caloric profitability (numerous harvests in the same patch) of these resources to sustained human predation. Productivity itself cannot affect human temporal social dynamics if the resource is swiftly depleted within a specific patch after one or a few harvests. Archaeological records that show the body size of shellfish decreasing over time are usually interpreted to indicate intensive exploitation and the depletion of these resources, but there may be other explanations for such patterns. Therefore, the third aim was to compare temporal and spatial variations in the body size of Turbo sarmaticus in the MSA, Later Stone Age (LSA) and the present day, in order to investigate whether such variations result from human exploitation or environmental changes