Survival and Detection of Blood Residues on Stone Tools

Article excerpt

A new field is opening up in biological archaeology, as it is found that ancient DNA and other bio-molecules may - under the right conditions - survive over the long term. Is the some true of blood residues on stone tools?

Introduction

Archaeologists have long been interested in determining the functions stone tools served in their original context. The attempt to determine the species identity of blood residues on stone tools from archaeological sites is one such recent endeavour. The first efforts to identify blood residues on tools were made by Loy and colleagues who used crystallization (Loy 1983) and detection of iron from hemoglobin (Nelson et al. 1986); but these attempts are considered by others to be unsuccessful (Gurfinkel & Franklin 1988; Smith & Wilson 1992).

The next attempt to identify blood residues on stone tools employed a technique adopted from forensics, using an immunological reaction to antibodies to identify the source of bloodstains. When confronted with a bloodstain of unknown origin, the criminologist can determine whether it is human or from some other species of animal by observing which anti-serum it reacts with. Using forensic techniques, Newman & Julig (1989), Loy et al. (1990), Hyland et al. (1990), Yohe et al. (1991), Kooyman et al. (1992), Loy & Hardy (1992) and Newman et al. (1993) report having identified the species of origin of blood residues on stone tools or in rock-art pigment or coprolites. Nelson (1993) has recently retracted the identification of a substance originally reported as blood (Loy et al. 1990). Others have reported that using an immunoassay technique they were able to detect immunologically active proteins in fossil bones and tissues (Lowenstein 1985; Shoshani et al. 1985), and hemoglobin and albumin in human bones that have been buried up to several thousand years (Ascenzi et al. 1985; Cattaneo et al. 1990; Smith & Wilson 1990).

The reliability of immunoassay for archaeological material has been questioned in several reviews of immunological methods. Benjamin et al. (1984) note that antibodies raised against a native protein often do not react with the denatured form, contrary to the claim by Newman and co-workers (Newman & Julig 1989: 120; Yohe et al. 1991: 661). As Benjamin et al. (1984: 94) point out, conformational integrity, which is lost on denaturation, is critical to immunological activity, and the reaction with short unstructured peptide sequences has little significance.

Paabo et al. (1989) note that immunological methods are likely to give misleading results when used with poorly preserved material and question the value of antigenic studies on ancient substances; since archaeological material is old, and much is poorly preserved, this caution is valid for archaeological application. This criticism is especially applicable to work in which the proteins in ancient materials were not isolated and purified prior to their use in immunological testing.

Child & Pollard (1992), in a critical review directed at archaeological bone studies, but equally valid for blood residues on tools, note the following: using degraded material to produce antibodies in rabbits is immunogenically meaningless and only proves that host animals produce antibodies when stimulated. Because archaeological material is always degraded to some degree, all antigens and antibodies must be purified and tested for specificity. Child & Pollard recommend that immunological testing be considered a screening procedure, and identification of a specific protein considered positive only when confirmed by amino acid sequencing analysis. If this reasonable criterion is accepted, none of the reports in the literature can be taken as conclusive since adequate purification, and often controls, were lacking (apparently, since they were not mentioned), and in no case was a protein identified by amino acid sequencing.

An important concern for blood residue analysis is whether blood can survive in a biologically active form over long periods of time. …