Molecules on the Edge
This project involves the determination of blood residues on excavated stone tools from the archaic period and assesses the impact of storage, handling, and washing on molecular preservation. The materials that are the subject of the research are from the Tuban Cave, Israel. The cave contains evidence of more than 80,000 years of human occupation. Determining if the adhering material on the tools contain protein of lipids and if it is of human origin, this project will result in the formulation of guidelines for archaeologists and collection managers that optimize the preservation of such information on excavated objects.
In 1995, with funding from the National Center for Preservation Technology and Training of the National Park Service, examination was carried out of a assemblage of stone tools excavated from several sites, collectively called Barney Circle, along the Anacostia River in Washington, D.C. Parallel experimentation was performed on a set of experimental tools in order to examine the impacts that excavation, conservation and storage may have on stone tool and pottery artifacts as these materials make their journey from the archaeological site to the museum drawer. Two of the most common interventions, human handling and washing, severely and disadvantageously impacted both protein identification by immunological techniques and DNA amplification using the polymerase chain reaction.
For residue analysis to provide maximal information to archaeologists, alterations in excavation techniques, post-excavation processing and storage, and long term curation will have to dramatically change. While it is unrealistic to propose the all excavations and museum collections accommodate the special needs of molecular level research, select sites and collections will benefit from the consideration given to the friable nature of ancient biomolecules. A shift in perception that considers the inorganic remnants of past life as divorced from the ancient biosphere, and unaffected by present biota to a more inclusive and organic view will add to the interpretation of the archaeological record. At the Barney Circle site, multiple tools were identified with macroscopic residues adhering to the surface, and several different proteins were identified on the basis of molecular weight and immunological reactivity. In cases where protein was preserved on stone tool edges, the use of the tool on animal products can be assigned though the identification of the albumin molecule from blood. The amount of protein remaining after some 1500 years, is vanishingly small. Further surveys of tool assemblages from excavations where human handling was not permitted will form the basis of comparative work ongoing in the laboratory.