Before we begin discussing the scientific origin of the zombie, it is important that we take a bird's eye view of mythology and superstition in general. One need only turn on the television or visit the local library to understand what a key role these ideas play in all cultures. Richard Matheson's I Am Legend has been discussed a few times throughout this page, and I wish to bring it up again. The protagonist, Robert Neville, is attempting to study the vampires that he has to contend with on a nightly basis. Matheson touches on an extremely important point when he discusses how our perceptions of certain things are basically amalgams of all historical accounts. For example, in his studies, he finds that showing a vampire a cross only works in certain situations, ostensibly with those vampires who were once of the Christian faith. When he shows Ben Cortman a cross, there is no response. Upon showing him the Torah, however, Cortman reacts in typical vampire fashion, suggesting that there is no "magical power" associated with the cross specifically; rather, the reaction is a psychological one, and depends on each individual vampire and the faith they once belonged to. Thus, a Buddhist vampire would not have an adverse reaction to a cross, whereas a vampire previously of the Christian faith would have no reaction to, say, a Shinto symbol.

The point of all this is to say that we base our current paradigms on centuries of tradition, mythology and superstition. Some things are 100% accurate; in the case of zombies, head trauma is the most effective (and sometimes only) way to destroy them. Other things, however, are totally baseless. That said, let us examine one popular theory regarding zombification.

It should be noted that "zombie" can be applied to multiple classes of a thing. For example, we have the zombie of Haitian voodoo, which is basically a drugged and unaware human being. Take away the drug, and the human regains control of their ordinary faculties, minus any brain damage from prolonged usage of the chemicals. The term can also be applied, albeit rather loosely, to anyone who goes through the motions of their day (i.e., work, driving, making love, etc.) without any real emotional or mental involvement. However, neither of these "zombies" pose any real threat to us, so our focus must needs be elsewhere. The zombie threat can be narrowed down to those creatures whose bite, scratch, and indeed through other methods of fluid transfer, can lead to our own death and zombification. That said, our focus will remain there.

Let us begin by considering the way zombification is transmitted. To date, and by the grace of God, there are no known cases of airborne Infection. There have been studies where a team of scientists worked in the same room as a captured and restrained Infected for long periods of time with no adverse physical reactions. (Though the psychological effects of being around the undead for extended periods of time were not considered at the time, their repercussions were rampant).

The only known and recorded cases of Infection come from direct fluid to fluid transmission. That said, we can assume a few things. First of all, we can assume the method of Infection comes from something contained in the fluids being transmitted. The most logical assumption, then, is that a blood-borne organism, most likely a virus, is transferred from the Infected to the victim.

Assuming that Infection is spawned by a virus, let us now examine the medical aspect of Infection. Viruses live to propagate. Their method of attack allows for exponential growth; that is to say, if a virus infects one cell, it will split and infect two neighboring cells, which will infect four cells and so on. Eventually, a virus will take over a host unless antibodies and other aspects of the immune system are able to combat it. There are three specific stages of Infection, which we will now discuss.

The earliest stages of Infection occur from the onset to anywhere from a few days to weeks, depending on the health and constitution of the subject in question. During this stage, the subject's general health will decline noticeably. Symptoms may include nausea, fever, weakness and other flu-like symptoms. As the Infection progresses, subtle personality changes will take place. The patient will become cranky and snappish toward their friends and loved ones, be in a constant state of anger or violent depression, and will eventually become completely hostile and sometimes violently aggressive.

The real danger in early Infection is in these symptoms. Outside of the violence, these symptoms are, for all intents and purposes, indistinguishable from any other sickness, with the personality changes being attributed to the patient's discomfort. Thus, it becomes quite easy to let one's guard down and just assume that one is dealing with a commonplace "bug." This must be guarded against at all costs. In the final stages of Infection, the patient will lose all sense of self and become extremely violent, lashing out at any and all in near proximity. To quote a common media example, the zombies depicted in 28 Days Later are an excellent example of the final stages of Infection. It can be easily deduced from this alone as to exactly how our "modern day mythology" is a collection of ideas surrounding the zombie mythos, all touching on truth, but never quite telling the entire story. Again, if you have not read I Am Legend, do so.

The final stages of Infection invariably lead to the patient's death, be it from the virus completely taking over the central nervous system (CNS) or by other means, such as their destruction. It must be stressed that there is nothing magical or superstitious about the Infected "coming back from the dead." Any consciousness or, dare I say it, soul the Infected has is now gone, just as if they had died and were embalmed and buried as normal. At the point of death, it is of paramount importance that the brain be destroyed, either by severing the head from the body, burning the entire body (preferable), or any other means of causing massive trauma to the brain and CNS.

The virus, having now taken over the host's body in its entirety, has nowhere else to turn but out. As the virus's sole reason for existence is to propagate and spread, it now has only one source available - other hosts. As such, and given the virus's stranglehold on the CNS, the host body becomes activated by electrical impulses originating from the brain. The problem is that the virus is a newcomer to the body and is not "hardwired" and in tune with the body's dynamics and movement processes. This produces the slow, shambling, clumsy body that is so often seen in George Romero's body of work.

Doxkid: Umm...this is a bit off. Continuing the virus idea, we would have to guess that infection is lytic (Virus infects a cell, forces it to mass produce viruses until they explode the cell and it repeats.) It would have to be specialized in the CNS to really be effective, but that doesn't mean that it would take over the body. A virus is basically...well, there isn't really anything as stupid as a virus. They are controlled by nothing similar to a brian and are probably less intellegent than a bacteria. Thus, if it destroys the body until death, it wouldn't revive the person. Maybe, its specific targeting could destroy inhabition while lowering the brain's control of the heart, which would make bleeding out more difficult, but it wouldn't let them ignore getting an arm blown off.

StrykerPez: I agree, this isn't accurate. Zombies must adhere to laws of the world like everyone else. Once dead, a body will stay (mainly) dead. Reanimation is possible, but the damage done to the nervous system, muscles, and circulatory system would render the subject immobile and it would die again as soon as the life support was removed. My theory is the "living zombie." These were humans before a virus attacked the awareness and control center of their brains. They are still perfectly human in outward appearence and function; they still need to breathe, eat, sleep, etc. The expression "like a chicken with its head cut off" applies here perfectly. Chickens can and indeed have lived for long periods of time (months) after being decapitated if the brainstem is not cut off. They will attempt to eat, they will rest, they can walk and run. Like this, the zombie will continue to walk and search for food, but with less, much less, refined behavoir. They are not decomposing, however due to their lack of self preservation and pain receptors they may have open wounds, broken bones, even missing limbs.
These zombies, while just as mortal as you or me, would be far harder to kill than a normal person. Like drug addicts that fight off 10 police officers at one time, the zombie would have no sense of pain, and therefore be able to push his body to the breaking point, tearing muscles and breaking bones, or using his skull as a battering ram. As Doxkid said above me, the heart would not have to beat as hard or fast to supply the remmnants of the brain with oxygen and therefore make it harder to bleed out.Unless a bullet hit a vital organ, a zombie would not stop, and even then, the weakened primordial brain would continue to push the body until the lack of oxygen destroyed the muscles and nervous system. A fresh zombie would have the ability to run and climb and swim and speak, just like a normal human, but most likely not the knowledge to do it. The limited brain capacity of the infected would result in clumsy behavior and moans or grunts for speech. Most likely, a zombie's sight would be blurry, single chroma, or otherwise impared. The hearing and smell however could possibly be heightened.
Zombies of this type would have a limited life span. Althought instinctually driven to feed and drink, human and or animal flesh is not a balanced diet, and they would suffer from malnutrition. Infection of open wounds and sores would also be a concern. With no desire for medical attention, any physical damage would go unchecked. In cold weather they would freeze to death. They may even be driven to feed on each other, although instincts may prevent that.

See also:

• Deteriorating tissue impacts
• First Signs of a zombie bite
• First signs of a zombie outbreak
  
• Why hunt the living?
• Motor Skills
• Nonhuman Infection
• Possibility of "recovery"
• Psychological effects on the living
• Experimentations
  
• How are zombies created?
• How a zombie virus could arise
  
• Celestial Events