No two corpses rot alike, which is why four U.S. universities operate “body farms” to study decomposition of human remains under different circumstances (e.g., above ground, in shallow graves, in extreme heat or cold). Their findings are used by forensic anthropologists and law enforcement. Still, corpses go through five specific stages of decomposition, ending in skeletonization.
Stage 1: Fresh
The body begins to cool. Bacteria begin to break down the tissue, which in turn produces gases and substances that attract insects. This initial decay typically occurs from zero to three days after death in normal conditions, when the body is exposed to air, according to experiments by the Australian Museum.
Stage 2: Putrefaction
The body begins to bloat, owing to the gases that bacteria produce. These bacteria are the natural inhabitants of the colon, which begin to move through the vascular system. The face and abdomen in particular appear swollen. The skin becomes delicate and begins to break down and slough away. The skin goes through a series of color changes, from green to brown. Putrefaction typically occurs between four to ten days after death.
Stage 3: Black Putrefaction
The body becomes bloated enough to burst, allowing gases to escape (which occurs particularly around the abdomen). This opens the internal organs to attack by insects. At this stage the body’s organs will degenerate into a soupy mess. This occurs 10 to 20 days after death.
Stage 4: Butyric Fermentation
The wet stages of decomposition end, and the corpse begins to dry out. The odor associated with bacterial activity begins to dissipate, and the body becomes a dried, mummified husk. This occurs 20 to 50 days after death.
Stage 5: Dry Decay
The internal organs have largely disappeared, and the body enters skeletonization. Note: skeletons do not typically remain articulated (as they are in many movies). The connective tissue rots away and the bones fall into a pile, or scavengers scatter the bones. This occurs between 50 days and one year after death.
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