Here's Why Mummies Don't Decompose

Perhaps the most well-known mummy is that of King Tutankhamun, the teenage Egyptian pharaoh who was entombed some 3,300 years ago amid his piles of treasure. There's also Ötzi the Iceman, a 5,300-year-old mummy that was discovered in an ice cave in the Italian Alps. Yet, while the means of their mummification differed — Otzi was frozen by the natural elements, while King Tut's body was meticulously prepared — both corpses were remarkably well-preserved upon discovery. The reason is simple: They were both kept dry. 

Dead organisms decompose when their bodies are broken down by bacteria. Some of that bacteria is already living inside the organism before it dies. For example, there are the prokaryotic organisms in our gut which are critical for survival, as they help us convert food into its digestible components. But the bacteria living inside us and on our skin continue to feed even after we perish, breaking down the inorganic and organic materials they encounter. Thus, to preserve a body from decay, the body's bacteria must die as well. 

The simplest way to prevent bacteria from decomposing a dead body is by eliminating water from their environment. All life forms require liquid water to live, so dehydrating bacteria prevents them from feeding and multiplying. This process of dehydration is called desiccation, which is actually the first step of creating many types of fossils. It's also the reason Otzi was naturally mummified — frozen in a flash and suspended in solid ice for well over 5,000 years, his bacteria was killed along with him. King Tutankhamun was desiccated as well, but without sub-zero temperatures to work in, his royal embalmers had a much bigger project on their hands.

The ancient Egyptians knew that as soon as their deified leader perished, time was of the essence. First, they removed most of the internal organs by pulling them through small holes using hooked tools. The ancient Egyptians believed the removed organs were sacred, and they stored them in special jars. However, this practice also served to eliminate a large portion of the water and bacteria from the body. Next, the body was packed with natron, an absorbent salt used often in ancient Egypt, to draw remaining moisture from the body.

Other artificial mummies were desiccated in similar ways. For instance, the oldest-known artificial mummies in the world are the Chinchorro mummies of modern-day Chile, with the earliest specimen dating back to 5050 B.C. Chinchorro mummification practices followed the same fundamental process as the ancient Egyptians. Organs were removed, and most of the remaining moisture was drawn out using ash and clay.

Once the body is free of moisture, it needs to stay that way. Artificial mummies were stuffed and wrapped with cloths, dry reeds, and anything else that might help create a barrier between the corpse and moisture. The ancient Egyptians also used hydrophobic chemicals, including tree oils, animal fat, beeswax, and resins, as an extra line of defense. Finally, the body was often sealed in a coffin. Air carries moisture, even in the desert, so the coffin had to be as airtight as possible. For ancient Egyptian royals, the wooden coffin was sometimes placed in a stone sarcophagus, which strengthened the seal even more. If such measures seem like overkill, consider how well they worked. King Tutankhamun was so well-preserved, scientists have been able to extract his DNA, diagnose him with malaria, and determine he had a club foot — not too bad after 3,300 years.