Ancient Egyptians used sophisticated combinations of natural substances to embalm the human body. Over time, they modified their recipes to balance quality of preservation with cost and availability of materials.
Over the years, scientific examinations of mummies have taught us a great deal about embalming practices, funerary rituals and burial economics in ancient Egypt. But that knowledge has often come at the cost of damaging the specimen. Mummies are an irreplaceable archaeological resource (Fig. 1), and these days the challenge is to extract new information without harming them.
On page 837 of this issue1, Buckley and Evershed show how a great deal can be learned from virtually non-destructive analyses of mummies. They reveal that Egyptian embalmers used a greater variety of natural materials than previously reported, and that cheap and readily available plant oils and animal fats were probably used as bases for more costly and exotic resins.
The Egyptians believed that no one could enter the afterlife unless the most important part of the spirit, the ka, could return to the body. So the dead body had to be protected from decay and preserved in a recognizable and life-like form. After centuries of experimentation, embalmers learned that they could achieve excellent preservation by removing decay-causing organs (the intestines, liver, lungs and stomach), and by treating the body with substances, such as salts, resins, cedar oil, palm wine, myrrh, cassia, gum, honey and bitumen, that had drying or antimicrobial properties.
Embalmers treated their clients according to what their families could afford: pharaohs were mummified with expensive mixtures and specially woven linen, but the poor received only cheap purges before being sent home to be wrapped in old clothes and used sheets. Depending on the wealth of the family and the customs of the time, mummies were buried in coffins (made of wood, fired clay or stone) or laid in communal pits. Both the materials and the various treatments used are described by ancient historians such as Herodotus2 (fifth century bc), and are supported to some extent by modern scientific analyses.
At the height of their art (tenth century bc or twenty-first dynasty; Fig. 2), embalmers mummified bodies so well that scientists today can occasionally recover DNA from tissue and hair samples3. Unfortunately, however, many mummies never survived past the nineteenth century. If they escaped attack by tomb robbers and collectors, they were ground up for medicine, used as fuel, or destroyed in public unwrappings conducted as entertainment4. And although some twentieth-century studies5,6 delivered a huge amount of information, they involved not only unwrapping a mummy but full medical autopsies, virtually destroying the specimens.
More delicate analyses pose several difficulties for chemists: there are only a few well-preserved mummies of known provenance and date; museum curators are reluctant to permit sampling of material; and embalming fluids become degraded over time.
Buckley and Evershed1 address some of these problems by using two complementary techniques based on a combination of gas chromatography and mass spectrometry. Their approach requires only tiny samples of tissue (less than 0.1 mg), and concentrates on diagnostic marker compounds that resist degradation. This essentially non-destructive approach conserves the artefacts and allows curators to comply with recent laws that require the respectful treatment of ancient human remains.
Previous chemical analyses of embalming substances confirmed the use of natron (a natural salt native to Egypt), juniper (rather than cedar) oil, camphor oil, myrrh, coniferous and other resins, galbanum (a gum resin) and beeswax7,8. Bitumen, a petroleum derivative, has also been reported in a few cases9. Buckley and Evershed's analyses identify the use of resins from conifers and Pistacia (another type of tree), coniferous pitch, balsam (perhaps), plant oils, some animal fats and beeswax. Widely available plant oils and animal fats were probably the base materials to which more expensive ingredients (resins, for example, some of which may have been imported from Lebanon) were added.
The authors point out that the amount of coniferous resins and beeswax increases in later mummies, implying that these substances became more important with time. They also stress the variety and compositional diversity of embalming materials. This finding is consistent with what other researchers have found: embalming materials and procedures vary more than expected, both within single dynasties and between historical periods10. This could be a result of economics (the cost and availability of materials), changing fashions, and/or the preferences of particular embalming guilds.
Buckley and Evershed tested 13 mummies of known provenance and date spanning approximately 2,300 years. However, only one or two mummies from each dynasty or period are represented (except for the Roman period, 30 bc to ad 395, for which four mummies were tested). Larger numbers of mummies from each period need to be analysed before we can conclude, for example, that Egyptian embalmers never used bitumen from the Dead Sea, or that bitumen was used only during the Roman period. (If this substance was used exclusively during Roman times, perhaps the reason was that it was cheaper or easier to transport under Roman rule.) Ideally, these mummies should be selected from those of known provenance and date to provide maximum information, but this is by no means easy — many mummies now residing in museums around the world are woefully deficient in documentation. In some cases, such as Roman mummies that can be dated fairly precisely by the style of the accompanying portraits, chemical analysis could contribute to our knowledge about embalming practices during a particular period without knowing the specific site of the mummy's origin.
As more mummies are tested, a larger database of embalming substances from all periods will help archaeologists explain variation in terms of changing economics and customs, as well as knowledge of material properties. For example, a preference for scented cedar oil over juniper oil in a particular period might indicate a choice based on fashion and cost, rather than preservative properties. The two coniferous oils are similar, but juniper oil was presumably cheaper to import from Lebanon because juniper was a more common tree than cedar. Wealthy Egyptians may have deliberately chosen the more expensive embalming fluid to impress family and friends, just as well-to-do people today select exotic woods and metal trims for their relatives' coffins.
Buckley, S. A. & Evershed, R. P. Nature 413, 837–841 (2001).
Herodotus The Histories (trans. de Sélincourt, A.) Book II, 160–161 (Penguin, London, 1954).
Pääbo, S. J. Archaeol. Sci. 12, 411–417 (1985).
El Mahdy, C. Mummies, Myth and Magic 24–51 (Thames & Hudson, London, 1980).
David, A. R. (ed.) The Manchester Museum Mummy Project (Manchester Museum, 1979).
Fleming, S., Fishman, B., O'Connor, D. & Silverman, D. The Egyptian Mummy: Secrets and Science (University Museum, Philadelphia, 1980).
Coughlin, E. A. Paleopathol. Newsl. 17, 7–8 (1977).
Benson, G. G., Hemingway, S. R. & Leach, F. N. in The Manchester Museum Mummy Project (ed. David, A. R.) 119–131 (Manchester Museum, 1979).
Proefke, M. L. & Rinehart, K. J. Am. Mass Spectrom. Soc. 3, 582–589 (1992).
Ikram, S. & Dodson, A. The Mummy in Ancient Egypt: Equipping the Dead for Eternity 109 (Thames & Hudson, London, 1998).
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