Once the soft tissues have fully decomposed, all that remains is the skeleton. The skeleton and teeth are much more robust. Although they undergo a number of subtle changes after death, they can remain intact for many years.
The last stage is when all byproducts of decomposition have dried up and only the skeleton and perhaps some hair are left. Beetles and flies eat anything softer that remains, and mites and moth larvae digest the hair. Exposed to the elements, the bones lighten in color and are eventually reclaimed by the earth.
This usually begins in the liver, which is rich in enzymes, and in the brain, which has high water content. Eventually, though, all other tissues and organs begin to break down in this way.
Bones do decay, just at a slower rate than other organic material. Depending on the conditions, this process usually takes a few years. Bones are largely a fibrous matrix of collagen fibres, impregnated with calcium phosphate.
However, on average, a body buried within a typical coffin usually starts to break down within a year, but takes up to a decade to fully decompose, leaving only the skeleton, Daniel Wescott (opens in new tab), director of the Forensic Anthropology Center at Texas State University, told Live Science.
After four weeks the body has begun to liquefy, with everything breaking down. Nails and teeth fall out.
3-5 days after death — the body starts to bloat and blood-containing foam leaks from the mouth and nose. 8-10 days after death — the body turns from green to red as the blood decomposes and the organs in the abdomen accumulate gas. Several weeks after death — nails and teeth fall out.
So, does hair decompose in soil? The answer is yes, but it decomposes very slowly. It can take anywhere between 1 and 2 years for natural human hair to break down completely in soil. This slow decomposition rate is due in part to the fact that hair is not very porous, which means that it doesn't absorb water well.
If you are looking at a long-lasting ground casket, pick a steel or metal casket. If the grave site is low on water content or moisture, metal caskets are known to last even longer, over five decades. Under favorable weather conditions, experts say that metal caskets may even last more than that – up to 80 years.
"Teeth tend to survive well. Some for tens of thousands of years," she says. Dental remains are a common feature in archaeological digs, although often many teeth are missing - they may have been lost prior to death, dropped out or they may have been lost in the excavation process.
What's really returned to you is the person's skeleton. Once you burn off all the water, soft tissue, organs, skin, hair, cremation container/casket, etc., what you're left with is bone. When complete, the bones are allowed to cool to a temperature that they can be handled and are placed into a processing machine.
Bodies decompose fastest in hot and moist environments. With higher temperatures, the bacteria in a body produce gas at a faster rate which creates more openings in the skin for flies to lay their eggs. Heat also helps break down cell structures and the liquification of bodily fluids occur in a shorter timeline.
For the most part, however, if a non-embalmed body was viewed one year after burial, it would already be significantly decomposed, the soft tissues gone, and only the bones and some other body parts remaining.
Your brain is one of the first parts of your body to break down. Just a few minutes after death, its cells collapse and release water. Then other energy-guzzling organs follow. That night, microbes eat through your gut and escape into the rest of your body.
Enzymes start to digest cell membranes and then leak out as the cells break down. This usually begins in the liver, which is enriched in enzymes, and in the brain, which has high water content; eventually, though, all other tissues and organs begin to break down in this way.
Wooden coffins (or caskets) decompose, and often the weight of earth on top of the coffin, or the passage of heavy cemetery maintenance equipment over it, can cause the casket to collapse and the soil above it to settle.
Snatching dead bodies was common in many parts of England and Scotland in the early 1800s. Therefore, graves were always dug six feet deep to prevent body snatchers from gaining access to the buried remains.
By ten-years, given enough moisture, the wet, low-oxygen environment sets off a chemical reaction that will turn the fat in the thighs and bottom to a soap-like substance called grave wax. However, in drier conditions, the body could also be mummified – that's mummification without wrappings, or chemicals.
Human hair can provide structural support to the plants' roots as they help break down clumpy and thick soil. As human hair is also rich in oxygen, carbon, hydrogen, and sulfur, it makes it as good as bone meal, making them perfect for use in compost.
Although if the environment, microbial life and internment methods favor decomposition, it will be relatively quick. If the factors do not favor the process, hair can take tens of years before decomposing. There has been evidence of hair on human remains, professionally excavated, approximately 100 years since burial.
On average, the lifespan of a human hair is 2 to 7 years. The hair on our scalp goes through 3 phases, the anagen phase, catagen phase, and telogen phase. The cross-section of a hair strand is made up of 3 key layers.
A study carried out by researchers at Australia's first 'body farm' also found that corpses can move during the decay process. And it's more than just a twitch. They found that movement occurred in all limbs after death, including in the advanced decomposition stages.
They might close their eyes frequently or they might be half-open. Facial muscles may relax and the jaw can drop. Skin can become very pale. Breathing can alternate between loud rasping breaths and quiet breathing.
Over time, coffins underground will decompose and eventually collapse. Covering the face before closing the casket adds an extra layer of protection and dignity for the deceased's face and can act as a symbolic final goodbye.