The role of geophytes in stone age hunter-gatherer subsistence and human evolution in the greater cape floristic region

It has been hypothesised that an adaptive shift to a starch-rich diet was an important driver in human evolution and supported the energetic requirements to sustain brain development throughout hominin evolution. Plants that possess underground storage organs (geophytes) have been put forward as the likely source of starch. Geophytes comprise a large portion of the plant diversity in the Greater Cape Floristic Region (GCFR), where significant archaeological evidence of the evolution of human modernity has been identified in the Middle Stone Age (MSA). It is thought that the resources available in this region during this time period fuelled the progression and development of complex language, art and tool production in early modern humans. The overall objective of this thesis is to determine the importance of geophytes in early modern human diets and the impact they might have had on human behaviour and cognition. The role of geophyte resources in Stone Age hunter-gatherer subsistence was evaluated by firstly creating an ecological and environmental framework of data to evaluate the geophyte resource base. Secondly, the archaeological evidence available on actual hunter-gatherer foraging behaviour was evaluated using this framework, together with novel methods of macrobotanical analysis and experimental archaeological methods. It was found that the nutritional quality of geophytes is high, even in comparison to domesticated crops such as potatoes. The desirability of geophytes to a forager would rely on many factors, apart from nutritional quality, however. Geophyte resources on the coastal plain of the GCFR are dense and diverse. This diversity encompasses variation in the quality of the nutrients contained in the USOs and the optimum time throughout the year they would be most profitable to harvest. Geophytes could have been available during a large portion of the year throughout the GCFR. The archaeological evidence shows just how widespread and complex geophyte foraging and processing were during the Holocene, although there is a relative lack of evidence in the MSA. The novel method presented to determine the energy cache offered by geophytes and the seasonality of geophyte foraging shows great promise to improve our understanding of foraging choices and hunter-gatherer mobility across the region. All Stone Age processing methods tested experimentally improved the nutritional quality of USOs, but veldfire produced the most profound nutritional quality improvements of all methods tested. Geophytes could have supplied the dense and predictable resource cache that made the GCFR a reliable environment for human evolution, despite climatic and vegetational shifts. The efficient exploitation of geophyte resources throughout the Stone Age could have altered early human behaviour and cognitive development

Modern soil phytolith assemblages used as proxies for paleoscape reconstruction on the South Coast of South Africa

South Africa continues to receive substantial attention from scholars researching modern human origins. The importance of this region lies in the many caves and rock shelters containing well preserved evidence of human activity, cultural material complexity and a growing number of early modern human fossils dating to the Middle Stone Age (MSA). South Africa also hosts the world's smallest floral kingdom, now called the Greater Cape Floristic Region (GCFR), with high species richness and endemism. In paleoanthropological research, improving our capacity to reconstruct past climatic and environmental conditions can help us to shed light on survival strategies of hunter-gatherers. To do this, one must use actualistic studies of modern assemblages from extant habitats to develop analogies for the past and improve paleoenvironmental reconstructions. Here, we present a phytolith study of modern surface soil samples from different GCFR vegetation types of the south coast of South Africa. In this study, the phytolith concentration and morphological distribution are related to the physicochemical properties of soils, the environmental conditions and the characterization of the vegetation for the different study areas. Our results show that phytolith concentration relates mostly to vegetation types and the dominant vegetation rather than to the type of soils. More abundant phytoliths from Restionaceae and woody/shrubby vegetation are also noted from fynbos vegetation and grass phytoliths are a recurrent component in all the vegetation types in spite of being a minor component in the modern vegetation. The grass silica short cells from these plants, however, suggest a mix of C3 and C4 grasses in most of the vegetation types with a major presence of the rondels ascribed to C3 grasses. The exceptions are riparian, coastal thicket and coastal forest vegetation, which are characterized by the dominance of C4 grass phytoliths

Underground storage organs of plants as a food source for Pleistocene hunter-gatherers in the southern Cape

Thesis (MSc)--Stellenbosch University, 2013.ENGLISH ABSTRACT: The abundance and diversity of carbohydrate and protein resources in the southern Cape of South Africa may well have aided the survival of modern humans through the harsh climatic conditions of the late Pleistocene. Until now, the carbohydrate resources, in particular the underground storage organs (USOs) of some plant species have not been described from a forager’s perspective. This is baffling when one considers that the Cape Floristic Region of South Africa harbors the highest diversity of geophyte (herbaceous plants which possess USOs) species in the world. I report on USO distribution and abundance in the southern Cape of South Africa and on the effort, nutritional return and energetic return rates of harvesting these USOs. To determine their distribution and abundance, I assessed identity and abundance in a hundred 25m2 plots. These data, along with biomass data of every species sampled, allowed me to quantify the variation of this potential food source over different habitat types in the southern Cape landscape. Furthermore, I observed the time it took for human subjects to gather a sample of six USO species in three different vegetation types and in two seasons. Proximal analyses of the nutritional content of each of these species provided data which, when combined with foraging time, enabled a basic quantification of the return rate of energy (in calories) per time unit. There is high variability in the distribution of edible USO abundance and biomass across the study area, with some sites having very high biomass. Such biomass hotspots are likely to have been targeted by foragers, returning biomass values comparable to other studies which have been conducted on extant hunter-gatherer communities. Due to considerable variation over the landscape, the hotspots of biomass did not correlate significantly with any abiotic variables we measured. This suggests that hotspots of high biomass may have been challenging to find, unless the cognitive skills required to locate such patches were sufficiently developed – certainly excellent knowledge of the landscape and botany would have been crucial if survival depended on locating these diet items. USO species belonging to the Iridaceae family had the highest overall and average biomass in the area, so it is not surprising that this family is best represented amongst USO plant remains found in the archaeological record. Little effort (time) was required to obtain the six species of USOs we observed, although the weights obtained were also low. The nutritional returns of the six test species were higher than in other studies. The return rates per simulated foraging event in this study therefore compare favorably to the anthropological observations of extant hunter-gatherer communities. The lines of evidence presented in this thesis therefore lend support to the hypothesis that the USO resources of the southern Cape would have provided a large component of the carbohydrate requirements for sustaining hunter-gatherer communities. The data set presented in this thesis can be considered a baseline for future studies.AFRIKAANSE OPSOMMING: Die digtheid en diversiteit van koolhidraat- en proteïenhulpbronne in die Suid-Kaap van Suid-Afrika mag die oorlewing van die moderne mens beïnvloed het tydens die ongunstige klimaatstoestande wat geheers het deur die laat Pleistoseen. Tot op hede is die koolhidraathulpbronne in die area nie beskryf vanuit ‘n kosversamelaar se perspektief af nie, spesifiek nie die koolhidrate wat deur ondergrondse stoororgane (OSO's) van sommige plantspesies verskaf kan word nie. Dié feit is verstommend as mens in ag neem dat die Kaapse Floristiese Streek van Suid-Afrika die hoogste geofietspesies (kruidagtige plante met OSO's) diversiteit ter wêreld het. Ek rapporteer oor die verspreiding en digtheid van OSO's in die Suid-Kaap en op die inspanning, voedingswaarde en energie-opbrengskoerse verbonde aan die oes van dié OSO's. Verspreiding en digtheid is bepaal oor ʼn honderd 25m2 plotte. Dié data, saam met die biomassa-data van elke spesie wat geïdentifiseer was, is gebruik om potensiële voedselbronne te kwantifiseer in verskillende habitattipes in die Suid-Kaap. Ek het verder die tyd wat dit neem vir mense om die ses geïdentifiseerde OSO-spesies te oes in drie verskillende habitatte en twee seisoene waargeneem. Voedingswaarde-data, tesame met OSO-oestyd-data, is gebruik vir die basiese berekening van energie-opbrengskoerse van spesies deur middel van proksimale analises. Daar is hoë variasie in die verspreiding, digtheid en biomassa van eetbare OSO's gevind in die studie-area, met sommige plotte wat baie hoë biomassa bevat het. Hierdie areas van hoë biomassa sou heel waarskynlik deur kos-versamelaars geteiken gewees het, en gevolglik hoë opbrengste van biomassa bied, wat vergelykbaar is met die biomassa-waardes wat waargeneem word binne areas waar huidige jagter-versamelaar-gemeenskappe tans oorleef. As gevolg van die aansienlike variasie wat waargeneem is oor die landskap het die hoë-biomassa-areas nie beduidend gekorreleer met enige abiotiese veranderlikes wat gemeet is nie. Dit dui daarop dat hoë-biomassa-areas moeilik kan wees om te vind, tensy kognitiewe vermoëns wat noodsaaklik is om kolle van hoë biomassa te vind ontwikkel was. OSO-spesies wat aan die Iridaceae-familie behoort het die hoogste algehele en gemiddelde biomassa in die area gehad. Dit is dus nie verbasend dat dié familie die beste verteenwoordig word in die argeologiese rekord van OSO-plantoorskot nie. Min inspanning (tyd) was nodig om die OSO's van die ses geïdentifiseerde spesies te bekom, alhoewel die massa wat bekom is ook laag was. Die voedingswaarde-opbrengs (per eenheidsmassa) van die ses toetsspesies was hoër as in ander studies. Die energie-opbrengskoers per versamelingsgebeurtenis het gevolglik ook gunstig vergelyk met die antropologiese waarnemings wat van huidige jagter-versamelaars gemeenskappe gemaak is. Die resultate van hierdie studie ondersteun die hipotese dat die OSO-hulpbronne in die Suid-Kaap 'n groot komponent van die koolhidraat-vereistes van jagter-versamelaar-gemeenskappe sou gewees het. Die datastel wat in dié tesis aangebied word kan as 'n basisverwysing dien vir toekomstige studies

A stab in the dark: testing the efficacy of watsonia exudate as glue for stone tool hafting

Composite tool manufacture is a complex technological behaviour that arose in the Middle Stone Age. The hafting of stone tools to handles or shafts seems to depend on the use of glue or adhesive. Chemical and microscopic analysis of glue or adhesive residues on lithic artefacts show the origins of these residues to be from various plant and animal sources, although attributing these residues to specific species has been problematic for various reasons. Experimental evaluation of the efficacy of glue for composite tool manufacture is a valuable method to identify possible sources of residues found on lithic artefacts. Various plant sources of glue have been identified in historical accounts, but some are yet to be identified in the archaeological record or need to be tested for their efficacy. The botanical remains of the genus Watsonia are particularly well represented in the archaeological record, where it is thought to have been foraged as a food source by Stone Age hunter-gatherers. During field observations, Watsonia underground storage organs (USOs) have been found to produce exudate. We test the efficacy of this exudate as a hafting glue for stone tools. Our results indicate that Watsonia exudate is nearly as effective as resin from Vachellia karroo (previously Acacia karroo) trees. These results lay the groundwork for identifying glue as part of composite tool technological components in the archaeological record that may not yet have been identified by other analytical methods, and highlight the role USOs might have played in human technology