Natural mummies were created when bodies were preserved by environmental conditions that prevented decomposition. This happened because decomposers like bacteria and fungi, which need water to survive, were unable to break down the soft tissues in the body. Natural mummification typically occurred in extreme environments such as very dry deserts, acidic and oxygen-poor bogs, or freezing conditions in glacial areas. For example, desert sand absorbs bodily fluids quickly, deserts are very dry, bog water is acidic and lacks oxygen, and glaciers act as natural freezers that halt decomposition. These natural factors caused the bodies to dry out or freeze before decomposers could act, thus preserving skin, organs, and other soft tissues intact for hundreds or thousands of years.
In summary, natural mummies were not created by a deliberate human process but by accidental and favorable environmental conditions such as dryness, cold, or acidity that inhibited decay.