Eventually, the gases and liquefied tissues purge from the body, usually leaking from the anus and other orifices and frequently also leaking from ripped skin in other parts of the body. Sometimes, the pressure is so great that the abdomen bursts open. Bloating is often used as a marker for the transition between early and later stages of decomposition, and another recent study shows that this transition is characterised by a distinct shift in the composition of cadaveric bacteria.
Bucheli and Lynne took samples of bacteria from various parts of the bodies at the beginning and the end of the bloat stage. They then extracted bacterial DNA from the samples and sequenced it. Flies lay eggs on a cadaver in the hours after death, either in orifices or open wounds Credit: Science Photo Library. As an entomologist, Bucheli is mainly interested in the insects that colonise cadavers. When a decomposing body starts to purge, it becomes fully exposed to its surroundings.
Two species closely linked with decomposition are blowflies and flesh flies and their larvae. Cadavers give off a foul, sickly-sweet odour, made up of a complex cocktail of volatile compounds which changes as decomposition progresses. Blowflies detect the smell using specialised receptors on their antennae, then land on the cadaver and lay their eggs in orifices and open wounds.
Each fly deposits around eggs that hatch within 24 hours, giving rise to small first-stage maggots. These feed on the rotting flesh and then moult into larger maggots, which feed for several hours before moulting again. After feeding some more, these yet larger, and now fattened, maggots wriggle away from the body. Wriggling maggots generate an enormous amount of heat within the body Credit: Science Photo Library.
Under the right conditions, an actively decaying body will have large numbers of stage-three maggots feeding on it. Like penguins huddling in the South Pole, individual maggots within the mass are constantly on the move. But whereas penguins huddle to keep warm, maggots in the mass move around to stay cool. Vultures and other scavengers, as well as other large meat-eating animals, may also descend upon the body. In the absence of scavengers, though, the maggots are responsible for removal of the soft tissues.
Third-stage maggots will move away from a cadaver in large numbers, often following the same route. Their activity is so rigorous that their migration paths may be seen after decomposition is finished, as deep furrows in the soil emanating from the cadaver.
Every species that visits a cadaver has a unique repertoire of gut microbes, and different types of soil are likely to harbour distinct bacterial communities — the composition of which is probably determined by factors such as temperature, moisture, and the soil type and texture.
All these microbes mingle and mix within the cadaveric ecosystem. Flies that land on the cadaver will not only deposit their eggs on it, but will also take up some of the bacteria they find there and leave some of their own. And the liquefied tissues seeping out of the body allow the exchange of bacteria between the cadaver and the soil beneath.
When they take samples from cadavers, Bucheli and Lynne detect bacteria originating from the skin on the body and from the flies and scavengers that visit it, as well as from soil. Thus, every dead body is likely to have a unique microbiological signature, and this signature may change with time according to the exact conditions of the death scene. A better understanding of the composition of these bacterial communities, the relationships between them and how they influence each other as decomposition proceeds could one day help forensics teams learn more about where, when and how a person died.
For instance, detecting DNA sequences known to be unique to a particular organism or soil type in a cadaver could help crime scene investigators link the body of a murder victim to a particular geographical location or narrow down their search for clues even further, perhaps to a specific field within a given area.
To this end, researchers are busy cataloguing the bacterial species in and on the human body, and studying how bacterial populations differ between individuals.
Drones could be used to find buried bodies by analysing soil Credit: Getty Images. Wescott, an anthropologist specialising in skull structure, is using a micro-CT scanner to analyse the microscopic structure of the bones brought back from the body farm.
He also collaborates with entomologists and microbiologists — including Javan, who has been busy analysing samples of cadaver soil collected from the San Marcos facility — as well as computer engineers and a pilot, who operate a drone that takes aerial photographs of the facility.
I thought if they can do that, then maybe we can pick up these little circles. A decomposing body significantly alters the chemistry of the soil beneath it, causing changes that may persist for years. As well as releasing nutrients into the wider ecosystem, this attracts other organic materials, such as dead insects and faecal matter from larger animals. Initially, it kills off some of the underlying and surrounding vegetation, possibly because of nitrogen toxicity or because of antibiotics found in the body, which are secreted by insect larvae as they feed on the flesh.
Ultimately, though, decomposition is beneficial for the surrounding ecosystem. A dead body's minerals continue to leach into soil months after death Credit: Getty Images. There is no time for them to get used to the idea of losing someone they love.
The important thing to remember about this kind of death is it's often so sudden that the person who dies feels little or no pain. We can be relieved about that. Many people believe that when someone dies only the body dies.
It is just as if a glass bottle full of water broke, and the bottle became useless. The container is gone, but what's inside — the water — remains. The part of a person that's left after the body dies is often called the "soul" or "spirit.
No one really knows what happens to a person's soul after death. There are many different beliefs about that, and it's best to talk with your family to find out what they believe happens after our bodies die. Then you can decide what you believe. When someone we love dies, it hurts us. We feel sad that the person will no longer be around to talk to or to have fun with. That absence leaves a big hole in our lives. Maybe you had a pet that died. Remember the first few times you walked into the house after your dog or cat was gone?
It was strange not to have your pet there. Maybe you cried — that's OK. We need to mourn, or grieve, over losing people and animals and other things we love. But just like when you skin your knee, the first, intense pain will go away after a while. It takes time for your knee to heal, but it hurts less and less each day. It's the same when somebody dies. Like giving birth, dying is a bodily process with stages and recognisable progression. Also like birth, the speed of the process can vary from person to person.
Medical support is sometimes needed to make dying or giving birth as safe and comfortable as possible. As dying approaches, most people lose interest in eating and drinking. Dying people consistently lack energy. Sleep usually recharges our energy and can be part of recovery but, at the end of life, sleep gradually makes less impact as the body winds down towards dying. A dying person spends progressively less time awake.
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