Symbolism, including language, is widely viewed as an essential element of modern human behavior. Documenting the evolutionary origins of such behavior, however, has proven difficult. Ochre pigments (iron oxides) form a major part of the evidence used to interpret when humans began communicating through symbols. Excavations at Olorgesailie, Kenya; Karonga, Malawi; and Twin Rivers, Zambia have yielded ochre artifacts that may indicate very early occurrences of symbolism. Yet mineral pigments may also form naturally in archaeological sites, or may have technological rather than symbolic uses. This project will evaluate and further develop analytical approaches to the chemical "fingerprinting" of ochre artifacts and sources from these three African localities. Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry and Instrumental Neutron Activation Analysis to facilitate the matching of artifacts to source deposits, the doctoral student Andrew Zipkin (George Washington University), under the supervision of Dr. Alison Brooks, will demonstrate the extent to which human ancestors were willing to seek out and transport specific pigments. This project also will use color quantifying technologies to determine if Middle Stone Age humans exhibited color preferences in the ochres that they collected and modified. Color preference potentially suggests symbolic use of ochre since the meaning given to different colors, such as in national flags, is a well-known aspect of modern human behavior.
The dissertation's final aspect will be an experimental evaluation of proposed non-symbolic uses of ochre. The leading alternative explanation is that ochre was an ingredient in plant resin adhesives used to construct compound tools, like stone-tipped spears. In collaboration with material scientists, the investigators will measure the effectiveness of different ochre minerals in formulating adhesives to test if glue production rather than symbolic meaning could explain past ochre procurement choices.
The research will contribute to the development of international collaborations between American, Australian, Canadian, Malawian, and Zambian researchers, as well as outreach activities for the general public. The development of new analytical approaches for "fingerprinting" mineral sources will find broad application in usage not just by archaeologists, but also by art historians, state agencies investigating the illegal transport of stolen antiquities, and forensic scientists.
