3 SCIENTIFIC CONCERNS

The significance of historical questions must be carefully weighed against the obligation to conserve cultural materials and the complexities of biological research, particularly destructive sampling for genetic analysis. Minimally invasive visual or microscopic examinations that could provide sufficient historical evidence are often overlooked in favor of “cutting-edge” technologies. An interdisciplinary team should design protocols for biohistorical testing and consider whether the proposed analysis can accurately answer the historical question.

Researchers should be familiar with the unique properties of aged biological samples and fragile cultural artifacts. Bioarchaeological methodologies for extracting and analyzing ancient human DNA are destructive, and biological traces pose special challenges. Techniques for extraction and analysis of aDNA from stains on historically important textiles such as CHS's cloak have not yet been experimentally substantiated (Gaensslen 1999). Enough DNA must be extracted to permit multiple independent amplifications as well as external replication to confirm the presence of aDNA. Additional sample material should be reserved for future testing or the application of new techniques not available at the time of an initial study (Kaestle and Horsburgh 2002). The presence of blood on fragile cultural artifacts should be confirmed prior to destructive sampling. A suitable microscale Takayama crystalline test has not yet been developed for aged textile bloodstains (Gaensslen 1999).

Contamination from modern DNA remains a significant problem for aDNA analysis. Despite general agreement on standard protocols to prevent and detect contamination, aDNA researchers regularly experience failure rates of over 50% due to contamination problems. The cloak associated with Mary Lincoln has been extensively handled by museum staff and even worn by a society member in the 1930s (fig. 3); each has left contaminating DNA deposits on presumed bloodstains. Standard procedures developed for decontamination of aDNA samples from bone, including surface removal with sandpaper, soaking in bleach, or UV irradiation, can be inappropriate for other materials. A biohistorical investigator who requested permission to conduct Y-chromosome analysis of CHS's Lincoln relics included a testing proposal from a private laboratory that provides modern DNA analytical services for genealogists. Laboratories performing aDNA analyses must be physically separated from modern DNA facilities and dedicated solely to human aDNA extraction and analysis to avoid contamination (Kaestle and Horsburgh 2002).