Decomposition is a concept that tends to be overlooked within the zombie genre. It may be for the sake of sustained horror that this very natural process is omitted from almost all literature pieces pertaining to the zombie apocalypse genre. This article covers the Max Brooks zombie type
While zombies are undead corruptions of the natural world, they are not impervious to the laws of nature. Nature dictates that any living organism will begin to decompose upon its death. As zombies are dead outside of very limited and basic brain and motor function - no blood or oxygen is pumped through any of the organs -, they are susceptible to the natural process of decomposition, but the Solanum virus (the virus that turns infected humans into zombies) makes the bacteria and other organisms in the process of decomposition instinctively 'drive away' from the zombie, making its decomposition rate extremely slow.
What the process of decomposition means is that in the event of a zombie apocalypse the undead will ultimately fall to rot, meaning as time goes by their threat will decrease, although it takes years for zombies to 'die' by decomposition.
As is well known, zombies are reanimated human beings. Their bodies are thus prone to the same damage and decomposition that we are. They may be able to appear uninhibited by broken legs as an example, but the impact on their mobility cannot be denied nonetheless, much like a human. Likewise their bodies are dead, and as with any dead human being, they will be susceptible to decomposition.
Five general stages are used to describe the process of decomposition:
- Advanced Decay
The general stages of decomposition are coupled with two stages of chemical decomposition: autolysis and putrefaction. These two stages contribute to the chemical process of decomposition, which breaks down the main components of the body.
Weens upon death; the heart immediately stops pumping blood. The result is the drained bluish coloration of the body. This aspect is often accurately depicted in most works of zombie literature. Another side effect is that within 3-6 hours of death rigor mortis sets in, causing muscles to stiffen. Once again another accurate portrayal in zombies as characterized by their stiff shuffle. Once the heart stops, immediate chemical changes occur in the body. One of these is the loss of cell structural integrity. As the cells themselves breakdown they release enzymes into the body that immediately begin to attack the tissue around it. This becomes more profound in later stages of decay but early signs include blistering of the skin. This is yet another accurate characterization of zombies; the blistered skin.
Upon death, the levels of oxygen are depleted as the body is no longer able to circulate oxygen. So, 3-6 hours after living death the zombie may well be active but it will now have the common bluish skin tone and blisters.
At this point decomposition really begins to take its toll on the human body. This is also when zombies should - scientifically - start losing their mobility.
Within 24 hours after living death the early stages of bloating results in the - as the name suggests - bloating of the corpse as the buildup of gases accelerates. This early phase will also be when a zombie is at its most infectious as the expanding gases force liquid out of all the orifices - nose, mouth, ears, anus -, so physically handling even a dead zombie - one that has been shot through the head - could still infect you via its body fluids, although Solanum blood coagulates or hardens, partially minimizing this problem.
Within 48 hours human saviour (sp??)begins. Active decay or more commonly, putrefecation sets in. The skin now gets a marble-like appearance as blood is almost gone, exposing the veins beneath the surface. This is where zombie literature ends with accuracy. While we see zombies with marble-like appearances and flaking skin, decomposition seems to end here.
Putrefecation is characterised by the rapid loss of body mass, meaning fat, organs and muscles are all targeted. The skin will now turn a blackish-green hue and begin to fall off, exposing the environment around the zombie to an outpouring of putrified fluids. This itself will be at near toxic levels, enough to kill vegetation and poison most animal species.
Depending on the environment this process can occur at an accelerated rate - think high temperatures and high humidity - or proceed at a slower rate - think winter and any area prone to sub-zero temperatures.
Simply put, within 5-11 years (at the most) of reanimation a zombie will likely no longer be mobile and almost certainly incapable of any sort of aggressive physical behavior. At this point the only dangerous thing about a zombie would be if a survivor absent-mindedly walked into one.
At this point activity around the corpse subsides. For all intents and purposes the zombie is no longer a threat whatsoever and is almost certainly no longer active.
Within several years the zombie will be no more than a skeleton with traces of skin.
Consequences of decomposition on the genre
If the laws of nature were accurately followed in the instance of decomposition, it is easy to see the effects it could have on that appeal of the genre. The zombie genre is built on the foundation of surviving hordes of the undead, yet as can be seen with regards to the the process of decomposition, a single zombie will no longer be an active threat after 4 days, largely minimizing the appeal of survival.
The above breakdown, however, only pertains to a single zombie, not a horde or a city of them, but the effects will be of a similar nature. Most pieces of literature all follow the same trend; first reports and cover-ups, increasing frequency and then the outbreak. The time-frame between increasing frequency and outbreak is rapid and once the point of outbreak is reached, infection is at rapid & uncontrolled levels. This all means that at the point of outbreak large portions of the population are infected almost simultaneously. The timeline in The Walking Dead indicates that within ten days - the period of Rick Grimes comatose state - the living population is almost eradicated. Within ten days not only will the living be almost extinct but the hordes of the early outbreak would themselves be largely neutralized by decomposition.
This does not say that the virus itself will be eradicated or eliminate any chance of isolated pockets of zombies - those in hospital/state morgues, those in colder climates - nor does it mean that a zombie outbreak will not be apocalyptic in nature and push humanity to the brink of extinction, but it does mean that should one survive beyond the first week of an outbreak, they will find themselves in the home stretch as the zombie population would be drastically and rapidly reduced. And as the mass outbreak would have already infected the majority of the world's population, the chances of the outbreak ever reaching such levels again is nonexistent.
The conclusion is that if the course of decomposition was accurately followed, it would have a very negative impact on the genre as it will nullify one of the appeals of the genre.