The 7th and final stage of decomposition, skeletonization, begins when soft tissue has dried and decayed to the point that parts of the skeleton are visible. Skeletonization is complete once all tissue has decomposed and all that is left of the corpse is bone. Remains may become reduced to bone in as little as three weeks but can take up to several years. Factors including temperature and environment determine the timeline of skeletonization. In a tropical climate the body may be reduced to bone in just a few weeks, in tundra, the process will take several years. Skeletonization may never occur if the corpse is in an environment with persistent subzero temperatures as seen in bodies left behind on Mt. Everest.
Instead of decomposing, remains of climbers who perished have been preserved due to the extreme cold and now act as trail markers up the treacherous mountainside. The bodies of those who die on Mt. Everest usually remain because an attempt to reach and recover the corpse would most likely prove to be unsuccessful, possibly resulting in another fatality. When the corpse is left in a peat bog or salt desert, skeletonization may be delayed, or natural embalming or spontaneous mummification can occur. The body may saponify, or become “adipocere” if left in certain environments, including a peat bog. This is a rare form of spontaneous mummification seen in the Mutter Museum’s “Soap Lady” who saponified in an alkaline, warm environment which was lacking air. While it is not common, it is possible for a corpse to undergo skeletonization in one area of the body, while experiencing some form of natural preservation in another.
In an area void of scavenging animals, bodies buried in acidic soil will take approximately 20 years to complete skeletonization and for bone to decompose to the point that practically no evidence of the body is left. In soil with a neutral PH level, a corpse can last as long as 100 years before bone has decayed almost completely. There is also a possibility bone may not deteriorate and the skeleton could instead become a fossil or crude oil.
Read about the Stages of Decomposition leading up to Skeletonization Stage 1: Pallor Mortis, Stage 2: Algor Mortis, Stage 3: Rigor Mortis, Stage 4: Livor Mortis, Stage 5: Putrefaction, and Stage 6: Biotic Decomposition
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If you enjoyed this article, you may also like Pray the Decay Away: Incorruptible Corpses and Other Forms of Natural Postmortem Preservation, Everybody Poops: The Post-Mortem Edition, Demystifying the Process of Dying and Burying the Dead is Killing the Planet.