Ancient Egyptian mummies stand as emblems of the chemical prowess of natural compounds for preserving human remains. Because Egyptian belief held that it was necessary for a part of the spirit known as the ka to return to the body to facilitate entry into the afterlife, embalmers honed techniques of mummification to maintain the body in a life-like form long after death. Now Stephen A. Buckley and Richard P. Evershed of the University of Bristol, writing in this week's Nature, provide a detailed chemical analysis of the compounds those Egyptian embalmers used.

The scientists examined 13 mummies spanning more than 2,000 years, including the peak period of mummification around 1,000 B.C. Using a combination of gas chromatography and mass spectrometry, the scientists searched for organic compounds resistant to degradation that serve as markers for specific balms and embalming agents. The diversity of materials used by the ancient embalmers, they determined, is greater than previously reported. In an accompanying commentary, Sarah Wisseman of the University of Illinois notes that this "could be a result of economics (the cost and availability of the materials), changing fashions, and/or the preferences of particular embalming guilds."

The team also tracked the evolution of embalming. "The use of drying oils was clearly widespread," they write, "with coniferous resins and beeswax increasing in importance with time." Coniferous resins, the scientists explain, can slow microbial degradation, whereas beeswax has antibacterial properties and serves as a sealant. Given that no detailed written records of the process exist, the findings shed much needed light on the role of organic preservatives in mummification.