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The Science of Zombism

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Because of their catatonic state, zombies have been unable to offer any personal testimony to augment scientific research. Therefore, all we know about them is based upon empirical evidence. A person infected with the zombism virus is transformed into a single-minded hunting machine, with all changes to bodily functions serving the zombic imperative: locate prey, capture prey and feed. Overall, the changes that take place in zombies are more limited than in vampires, since the virus infects and transforms far fewer tissue types than vampirism does (hence the smaller genome and shorter transformation). Specifically, the nervous and circulatory systems are drastically restructured, while more specialized modifications are made to the muscular and skeletal systems.

Brain & Nervous System

This system has been of great interest to researchers, as zombic nervous tissue appears to have regenerative properties not found in humans or vampires, which is one reason why they're able to survive their gradual necrosis. Unfortunately, their cerebral atrophy leaves them functionally lobotomized, and their hardy nervous systems remain just as vulnerable to electricity.

The brainstem is the only vulnerable region of the zombic brain—specifically the pons and medulla.

Brain: Contrary to most fiction, zombies are able to survive an enormous loss of brain tissue, as long as the lower brainstem remains intact. For instance, former FVZA zombie specialist Dr. Waxman Himmelburger tells of encountering a zombie who had lost over three quarters of its cranium from a shotgun blast, with no apparent effect. However, blindness can be inflicted by destroying the thalamus, occipital lobe or midbrain (which also causes deafness), while balance and fine motor control can be inhibited by targeting the cerebellum. Damage to the frontal and temporal lobes only result in a premature loss of what little intelligence and memory zombies start out with, while the parietal lobe simply reduces vision and physical sensation. As for a zombie's powerful sense of smell, the fact that the limbic system is anchored to the brainstem (via the hypothalamus) makes olfactory function extremely difficult to disable. Taste is even more resilient, thanks to its close connection to the medulla oblongata. This advanced form of neuroplasticity makes sense, considering how necrotic the brain becomes and how poorly zombies can defend themselves against cranial trauma.

This image from AMC's The Walking Dead shows the proper trajectory for a frontal headshot. Going straight through the mouth also works, as does the ear canal or the base of the skull.

Serotonin: As with vampires, zombies possess very little serotonin activity. Their lack of intelligence and restraint only make them that much more aggressive.

Dopamine/Endorphins: The smell and taste of living flesh trigger a large release of these adrenaline-like neurotransmitters into the zombic brain. Unlike vampires, zombies are largely unaffected by mind-altering drugs, as most of their compatible brain functions are inactive.

Circadian Rhythms: As with humans, zombies tend to sleep at night. However, it's fitful at best, as they will doze off for an hour or two, awaken, and doze off again, with lots of twitching and groaning and apparent nightmares.

Memory: As a result of brain damage sustained during the coma's high fever, the window for learning is only open a crack to begin with, and it closes rapidly after transformation, due to poor circulation and liver/kidney function. Within the first two to three days, a zombie can operate simple machinery and even drive, as well as learn simple activities such as pumping gas and using a key to unlock a door. But their ability to learn goes downhill fast as they decompose and experience a steady loss of grey matter. Learning new things becomes well-nigh impossible for them because their short-term memory is the first to go. Melee weapons are also within early zombic capabilities—and even firearms, though their aim is very poor and they rarely have the mental faculties to reload once the weapon runs out of ammunition.

Spine/Nervous System:
Zombies have exhibited the ability to withstand significant trauma to their central and peripheral nervous system. In a famous series of experiments conducted by FVZA scientists in 1972, zombies who had their spinal cords severed—and then laid on their backs—regained the ability to walk within 24 hours. Zombies who were laid on their bellies took at least 72 hours to regenerate, since less blood was able to pool in their spinal nerves. Although researchers have been unable to unlock the exact mechanism for this process of repair, massive stem cell production and the absence of obstructive glial scarring are definitely key elements. Limited regeneration also occurs in the lower brainstem, though it's somewhat slower due to the higher complexity of its neurons. As for medical applications, there is hope that this process can be harnessed to reverse the effects of brain damage and paralysis in humans.

Reflex Action: Severed zombie heads are still capable of blinking, flaring nostrils, moving lips, making expressions, and even biting, up to one hour after the brain loses consciousness (which doesn't occur until a full minute after decapitation, compared to just a few seconds for normal humans, and up to 30 seconds for vampires). Comparatively, reflex action occurs in humans for only 30 seconds, and in vampires for up to 5 minutes. Interestingly, once all the blood oxygen has been used up, the onset of brain death seems to occur within a consistent time frame in all three species (roughly 5 minutes). As for other body parts, severed zombie hands can open and close for more than a minute after detachment.

Sense Organs

"Follow your nose" might be the zombic motto, as their powerful sense of smell compensates for the weakness of their other senses.

Ocular close-up of an early-stage zombie

Sight: Due to degradation of the lens and cornea, zombies suffer from severe myopia. In addition, they are colorblind, the scleras are red with inflammation, and gradual cataract formation causes the pupils to become milky and white. In time, complete blindness will set in as the optic nerves degrade, the vitreous humor filling the eyeballs liquefy and leak out, and the tissues holding the eyes in place rot away, causing them to come loose and fall right out of their sockets.

Hearing: Infection, swelling, fluid buildup and eardrum perforation cause zombies to lose about 50 percent of their hearing within a few weeks of transformation. Complete deafness sets in within another month as necrosis spreads further into the ear. Needless to say, zombies are poor candidates for ASL training, and it's unknown if modern-day cochlear implants could rehabilitate them.

Zombic ear canal prior to drum perforation

Smell: Zombies have even more olfactory receptors and limbic neurons than vampires, making their sense of smell approximately 25 to 30 times keener than a human's (compared to just 10 for vampires). If the wind is right, zombies can smell humans from as far as a mile away.

Taste/Touch: Contrary to some sources, zombies still retain some degree of physical sensation—similar to how a person's hand feels after laying on it for too long—with taste being the most prominent. Although their sense of pain is quite muted, zombies still suffer from chronic aching as their bodies break down. Decomposition sometimes causes the tongue to swell inside a zombie's mouth, blocking its airway; to avoid suffocating to death, it has no choice but to chew off or rip out the bloated organ.

Epidermis

Like bad apples, zombies mostly rot from the outside in, because their surface tissues receive the least blood flow and the most exposure to environmental trauma.

Skin mottling and ulceration in an early-stage zombie

Skin:
Pale and ashen, zombic skin appears bluer for Caucasians while Africans appear more grey, as with vampires. Decay sets in shortly after transformation, becoming more jaundiced over the course of a week as liver function degrades. Over the next two to three months, the skin becomes more mottled and flaky as infected, pus-filled sores erupt all over the body. Within a few more months, the sores become larger and more numerous, the outer layers of skin peel off, and the underlying tissues swell and become a putrid mix of green, grey, yellow, purple and black, before coming loose and sloughing off completely.

The extremities are the first to experience necrosis.

Photosensitivity: Although zombies aren't nocturnal like vampires, they will still seek shade when possible from harsh sunlight as their skin burns progressively more easily as they age and lose pigmentation, coupled with the fact that such burns take progressively longer to heal as their surface capillaries die off.

Hair/Nails: Early-stage zombies still experience growth to hair and nails, albeit to a much slower degree. It only goes downhill from there as toenails and fingernails start detaching from their beds and hair sheds from the extremities. As with vampires, the scalp is the last area to lose all of its hair, though the rate of hair loss occurs at a much faster rate (within the span of a year, as opposed to a decade). Like their teeth and jawbones, zombies will claw at their victims using their exposed finger bones long after their nails have come off.

Continue to Part II

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