Dissertation
Human signaling ecology: a case study of late Pleistocene mineral pigment assemblages from southernmost Africa
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2020
DOI: 10.17077/etd.005359
Abstract
This dissertation investigated whether early humans varied their use of symbolic technologies in relation to shifting social and ecological contexts during the Late Pleistocene in southernmost Africa. Symbolic technologies were defined in this project as any technology with implicit communicative potential – like paints, beads, and other ornaments. Late Pleistocene deposits produce some of the earliest instances of symbolic technologies in the form of ochres. Ochres are a range of ferruginous rocks and earth that can produce vibrant pigment powders when abraded. To date, the bulk of research on Late Pleistocene ochres has focused on the cognitive implications of their use – where the hominin using ochres exhibits complex cognition that qualitatively differed from earlier hominins. The capacity for ochres and other symbolic technologies to communicate social information, such as group affiliation or status, and the resultant demographic implications of their use, have been historically understudied, however.
To this end, ochre assemblages from three archaeological sites located on, or inland from, the southern coast of South Africa were explored in relation to local paleoenvironmental proxies. These sites – Pinnacle Point 5-6, Boomplaas Cave, and Knysna Eastern Head 1 – contain long records of human behavior that collectively sample the last 90,000 years. Ochre nodules from these assemblages were examined for size, geological characteristics, use-wear, and streak color. Results from this analysis were contextualized within a Human Behavioral Ecology framework. Within this framework, the Economic Defendability model predicts forager territoriality through an examination of the resource base in relation to its density and predictability, while Costly Signaling Theory suggests that information exchange should occur when the benefits of producing a signal should outweigh its production cost. It is hypothesized that larger and/or denser populations should favor increased signaling, since these contexts have more potential receivers of those signals and a forager can more easily offset the cost of signaling production through the relatively higher fitness imparted by group membership. Drawing on this hypothesis, this dissertation assessed whether ochre use intensified in periods when the Economic Defendability model suggests that we can expect larger, denser, or more territorial populations. Broadly speaking, results from this analysis suggested that foraging people on the coast intensified their use of ochres when local environments were highly productive and human populations were expected to be larger. Populations living inland showed less of a response to local environmental conditions, but instead appeared to have intensified ochre use in relation to regional environmental conditions.
The Economic Defendability model also produces predictions for forager mobility in differing environmental contexts. This dissertation tested the mobility predictions through the compositional and sourcing analyses of a small subset of ochres from Pinnacle Point 5-6 and samples from seven naturally occurring deposits in the study area. These samples were submitted to the Missouri University Research Reactor for Neutron Activation Analysis, X-Ray Diffraction, and Scanning Electron Microscopy – Energy Dispersive X-Ray Spectroscopy to characterize their elemental and mineralogical compositions. Results from these analyses suggest that the studied ochres likely came from one of three sources. Two of these sources are located within the study area. The third group did not match any of the local sources, suggesting that these ochres could have come from deposits outside the study area, or on what is now the submerged coastal platform just offshore. These results appear to support the mobility predictions of the Human Behavioral Ecology model, with the proportion of potentially non-local ochres increasing during contexts where foragers are expected to have increased their mobility, while the proportion of potentially non-local ochres decreased in contexts where populations were expected to be more sedentary.
Details
- Title: Subtitle
- Human signaling ecology: a case study of late Pleistocene mineral pigment assemblages from southernmost Africa
- Creators
- James R McGrath
- Contributors
- James G Enloe (Advisor)Matthew E Hill (Committee Member)Margaret Beck (Committee Member)Robert G Franciscus (Committee Member)Curtis W Marean (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Anthropology
- Date degree season
- Spring 2020
- DOI
- 10.17077/etd.005359
- Publisher
- University of Iowa
- Number of pages
- xxiv, 435 pages
- Copyright
- Copyright 2020 James R McGrath
- Language
- English
- Description illustrations
- color illustrations, color maps
- Description bibliographic
- Includes bibliographical references (pages 395-435).
- Public Abstract (ETD)
This study examined whether human population size or density changed during the Late Pleistocene in southernmost Africa, as indicated by the variable use of symbolic technologies recovered from archaeological deposits. Symbolic technologies are defined here as any technology with implicit communicative potential. This dissertation focused on the use of ochres (iron-rich rocks used to create vibrant pigments powders). The function of symbolic technologies is understood in terms of information exchange between two or more individuals. Changing environmental conditions throughout the Late Pleistocene would have resulted in shifting human population densities and territorial behaviors, which in turn would have prompted different degrees of information exchange to occur.
Three archaeological sites provide the case studies for this dissertation. These sites – Pinnacle Point 5-6, Boomplaas Cave, and Knysna Eastern Head 1 – collectively sample 90,000 years of human occupations in southernmost Africa and occur in different environmental contexts. Ochre assemblages from these sites were analyzed for specimen frequency, geological characteristics, and use wear. Results from this study suggested that ochre was used more intensively when local or regional environmental conditions were more productive. This likely relates to predicted increases in population sizes within productive environmental contexts. Changes in territorial range sizes accompanying these demographic shifts were also explored through the compositional analyses of ochres from Pinnacle Point 5-6 at the Missouri University Research Reactor. These analyses found a higher rate of local ochres when populations were expected to be more sedentary and increased rates of potentially non-local ochres when populations were expected to be more mobile.
- Academic Unit
- Anthropology
- Record Identifier
- 9983949496502771
Metrics
3 File views/ downloads
85 Record Views