4
White Walkers, Zombies, Parasites, and Statistics
Zombies are the vampires of the late 2000s and early 2010s, but they have a much richer history, having been a fixture in entertainment for many years. As with the vampires before them, zombies have a generally agreed-upon set of rules that writers follow, but the rules can be bent to suit the story. Heck, vampires go from being soulless, deadly assassins who die in sunlight to having a soul and falling in love with slayers to not only surviving in sunlight but sparkling. The rules are even more flexible when there’s romance involved. The same is true for zombies, with different narratives imposing different rules. With roots in voodoo, White Zombie (1932) is widely considered the first zombie movie and has very clear rules for how zombies behave. George A. Romero’s Night of the Living Dead (1968) is seen as the starting point for modern zombie lore as well as the idea of the “zombie apocalypse,” though the term “zombie” is never used in the film. With a few exceptions, the current boom of zombie films seems to feature creatures that are slow and lumbering, don’t have a zombie master of any kind, and are generally in search of brains (to eat—no Scarecrows here). The common factor, though, is that zombies are undead, meaning animated but not alive. They are controlled by something—either a puppet master figure or an insatiable craving for brains—and have some ability to move and attack.
Sounds a lot like some of our cold friends north of the Wall.
And just like the rest of America, scientists can’t seem to get enough of zombies. Of all the fictional monsters, I believe zombies are the most studied. There is research into the neurology, anthropology, statistics, mathematics, biology, and diet choices of zombies—so much research, in fact, that there is even a Zombie Research Society that collects and distributes all of this work.1 They have a very conservative view of what a zombie is (see the definition in the next section), but if you are looking for current research on all things zombie, this is the place to start. Unfortunately, their membership link is broken or I would have joined.
Zombies aren’t just fictional. Often, there will be headlines about “zombie raccoons” or “zombie wasps,” with articles discussing how an actual animal can turn into a zombie and what that behavior might look like. Numerous websites and research papers have been devoted to discussions on how to survive a zombie apocalypse. In fact, there is more than one zombie apocalypse survival kit available for purchase. With all this zombie love and lore going around, it is my hope that in this chapter I can put the wights and White Walkers of Game of Thrones in a “scientific” context. How do they operate? How do they move and fight? How does this compare to real-life zombie animals? Wouldn’t their bodies decay? Most importantly, what can current statistical research tell us about how to survive an encounter with the army of the dead if a few of us rogue adventurers were to find ourselves north of the Wall without dragonglass?
What Is a Zombie, and Do Wights and White Walkers Count?
This really does seem like it should be an easy question. Zombies are neither dead nor alive; they are generally decaying corpses; they want to eat brains; and they don’t have much coordination. It’s possible, however, to find an exception to every one of these rules. Disney zombies sing and dance, but this is ridiculous so I won’t discuss them further. According to the Zombie Research Society, zombies are defined as “a relentlessly aggressive human, or reanimated human corpse, driven by a biological infection.” They go on to state that “the zombie pandemic is inevitable, and survival of the human race is crucial. It’s simply a matter of when . . . so be prepared.” So, by their definition, zombies are aggressive and obey no master—they are driven only by the need to spread their infection. When it comes to zombies, it seems they can be sorted into classes based on a few key questions and attributes. The first question is: Who or what is controlling them? There are have been accounts of zombies either operating independently, as in Night of the Living Dead, or being controlled by a single person, as in White Zombie. Another question that needs to be answered is zombie motor skills. In the case of iZombie, they are able to control their motions and move with purpose almost like a normal human. In Night of the Living Dead, they are lumbering without clear, easy motion. The Walking Dead presents zombies somewhere in between. Different zombies can have different goals. Some zombies are specifically after brains or are aiming to turn others into zombies, as in World War Z, whereas others are seeking specific targets. These are usually the ones that are controlled by a master.
One of the key distinctions between classes of zombies is what causes the zombification and how it is spread. In modern lore, it is usually seen as a neurological disease that is spread through bites. Older zombies, however, were turned by their masters. When looking at the possibility of surviving a zombie apocalypse, it is important to know exactly how zombification may or may not spread. Rarely can zombies be cured. This is usually seen only in older zombie stories, but it is still part of zombie legend. Keeping all these things in mind, let’s look at how wights and White Walkers would be classified as zombies and determine whether we can apply the science of zombies to the army of the dead.
In the army of the dead, the White Walkers are the generals and the wights the foot soldiers. This is the master–zombie structure in line with the older zombie paradigm. Though unusual for zombies, it’s still well within canon. The wights maintain their ability to fight and, in the case of Benjen Stark, still have some understanding of who they used to be. Any discussion of their motion needs to take this into account. This type of zombieism isn’t an infection but a reanimation. Much of the scientific analysis around zombies treats the spread of zombieism as if it were an infectious disease, but that doesn’t apply here. Instead, it’s more of a hub-and-spoke model, which propagates far more slowly than if wights were able to create new wights on their own. This affects how quickly the Night King can build up his army. In the puppet master model, the goal of the zombies is set by the one that controls them. This is exactly like the setup in White Zombie. Just like those zombies, killing the master kills those that he turned. Unlike those zombies, though, wights must be killed in specific ways, and they cannot be cured. Though wights are not the zombie seen in more modern media, they are well within zombie canon and much of the research on zombies applies here.
Neurology and Biology of Zombies
As zombies took over pop culture, scientists began to contemplate both the possible neurology of a zombie and real-life zombie diseases and parasites. In these cases, they looked at real instances of one organism being controlled by another without realizing it as well as potential causes of standard zombie behavior. The addition of “zombie” to a headline is definitely going to bring in some clicks—take, for example, a recent story about “zombie raccoons” in Ohio. In this case, the raccoons were acting like zombies, walking on their hind legs and foaming at the mouth before falling into a comatose state. With the exception of the last part, that’s pretty typical of the modern zombie: zombieism with no master and unusual behavior. The videos, which include other animals such as coyotes and foxes, are really quite shocking. Dr. Tara Smith, a professor of epidemiology at Kent State University, discussed the issue with US national media, ultimately concluding that the animals were suffering from either rabies or distemper.
When wild animals act oddly, most people immediately assume rabies is the culprit. According to the CDC, there are 5,000–6,000 cases of rabies in the United States each year, but typically not more than five in humans (thank goodness). Because rabies spreads through saliva, outbreaks often occur locally. Bats are the most common carrier of rabies in the United States, and most human cases of rabies come from bats. You may not even realize you’ve been bitten in the event you come in contact with a bat, so if one happens to get into your house, make sure you get rabies shots even if you don’t think you need to.
Rabies can be seen as a zombie disease because the virus causes the host to behave in a way that will spread the disease. It causes aggressiveness, which makes the host more likely to bite, and because the virus lives in the salivary glands as well as in the nervous system, the aggressive behavior serves to transfer the disease. The virus enters the peripheral nervous system through a bite and travels through the nerves to the brain. No symptoms are present until the brain is reached, at which point the victim experiences nonspecific symptoms such as headache and fever. Brain swelling soon follows. From there, the disease progresses in two possible ways: furious rabies or dumb (paralytic) rabies. Those descriptions alone make the disease sound exactly like zombieism. The furious form is closer to modern depictions of zombieism, with victims afflicted by aggression, hyperactivity, a fear of water, and the inability to swallow. Death occurs within days of the onset of symptoms, usually from cardiorespiratory arrest. In dumb rabies, the victim is slowly paralyzed and slips into a coma. It’s safe to say that if the raccoons were suffering from rabies, it was the furious type. However, rabies doesn’t quite explain the raccoons’ unusual behavior.2
Dr. Smith also suggested that the raccoons could be suffering from a virus called distemper instead. If you have dogs, you know that they are typically vaccinated against both rabies and distemper every year. The distemper virus is different from rabies, but it can also cause neurological problems. Until recently, there were no recorded cases in raccoons, but distemper has been found to spread to a wide range of mammals (but not cats, luckily for them). It is much more infectious than rabies and can be spread through the air. It initially affects the respiratory and lymphatic systems and moves from there to the nervous system. Although the neurological symptoms resemble those of rabies, canine distemper virus operates on the nonnerve cells, or glia, of the central nervous system. The virus destroys a cell’s myelin sheath, a protective covering, which causes nerve damage, similar to how multiple sclerosis damages cells. Eventually, the animal’s brain swells and they begin to show outward signs of nerve damage. Because the disease affects different parts of the nervous system at different rates in every case, it’s hard to say how the disease will progress in a particular case. The destruction of the nerves in this way causes symptoms that mimic zombieism: head bobbing, rhythmic jerking of various muscles (usually the limbs), dilated pupils, watery and wonky eyes, loss of balance, and seizures. It’s no wonder people thought the infected animals had a zombie illness.3 Distemper is the most likely cause of the so-called zombie raccoons, and it causes zombie-like behavior, but rabies is ultimately a more zombie-like disease. It controls the host’s central nervous system and causes them to act in a way that spreads the virus.
There are examples other than rabies in nature that depict the puppet master variety of zombieism. Like the viruses, these zombie creators are trying to further their own reproductive ends. They take over hosts with the aim of creating a situation where they are more likely to reproduce. Technically, this is how the White Walkers use the wights—to kill and leave bodies for the White Walkers to reanimate, increasing the army’s numbers and moving the White Walkers closer to their goal of covering the world in ice. A parasite or other animal can invade and use the body of another organism to do its bidding. There are many examples of this in nature, one of which can even occur in humans. In fact, a huge percentage of those reading this book are probably under its spell. Because there are so many examples of parasites that create zombies, I’m only addressing my favorites, all of which operate through slightly different mechanisms.
Wasps are particularly good at controlling other animals. They are known to create zombies out of spiders, cockroaches, and caterpillars. The jewel wasp uses a neurotoxin to make a cockroach do her bidding. The wasp lands on the cockroach and injects a neurotoxin directly into the ganglion, which functions as the roach’s brain. The toxin is high in γ-aminobutyric acid, or GABA (more on this in chapter 13’s discussion of poisoning), which inhibits the roach’s ability to control its muscles. The roach doesn’t much care to run away, so it sits there and waits while the wasp builds a nest. The wasp then returns to the roach, eats the tops of its antennae, and then uses them as reins to guide the wasp to the nest. She then attaches an egg to the roach’s leg and seals it up. The egg hatches, eats the roach, and the whole thing starts over. The parasitoid wasp does something similar, only to caterpillars instead of roaches. This wasp makes the caterpillar both its incubator and ultimately mother figure. The wasp stings a caterpillar and lays roughly 80 eggs inside. As the eggs develop, they eat the caterpillar from the inside out, making sure to avoid vital organs so the caterpillar stays alive. After bursting out through the skin of the caterpillar, which lives through the ordeal, they build a nest and command the unfortunate host to keep watch over them. After the larvae are fully developed and they have no more use for their protector, the caterpillar dies and the wasps go off to do it all again. (There is a great National Geographic video of the process, but be warned: it is extreme nightmare fodder.) The mechanism for this zombification remains unclear. What is clear, however, is that nature can be really messed up.4
Being from Maryland and having had a small boat when I was a kid, I know all about crabs and barnacles. One is tasty with some Old Bay and washed down with Natty Boh (a favorite Maryland beer); the other is the bane of a boater’s existence. I hate barnacles with a passion, but if a crab could hate, its dislike for barnacles would far surpass my own. Sacculina carcini is a barnacle that hijacks the green crab’s reproductive system and uses it as its own. The barnacle lands on the crab and burrows into it through a hair follicle. From there, it sends tendrils throughout the crab’s body that are used to control its behavior. It then pushes out an egg sac and causes the crab’s reproductive organs to stop working and atrophy. Instead of trying to reproduce in normal crab fashion, it hangs out and distributes the eggs of the barnacle. Both male and female crabs can be infected and will behave like female crabs. Both male and female crabs treat the eggs of the attached barnacle the same way a female crab would treat her own offspring, with behaviors such as pushing clean water over them and protecting them from predators. The crab stops growing and regenerating its organs, but it can live for up to two years, producing more S. carcini. It’s pretty impressive that a barnacle can control a crab enough that it thinks it is producing its own children.
One of the most dramatic and well-reported agents of zombification is the fungi of the genus Ophiocordyceps. Although it’s debatable whether a fungus fully fits the definition of a parasite, in this case it certainly acts like one. It can affect many different types of insects, but the carpenter ant is particularly susceptible. The fungus infects the ant and causes it to climb to a certain height above the forest floor, lock onto a leaf, and stay there until the fungus sprouts a spore out of the ant’s head. These then rain down on the other ants below, propagating the fungus. Until 2017, how the fungus was capable of mind control was unclear because the ant’s brain did not contain fungal cells. It turns out that the fungus wasn’t controlling the ant’s brain but rather its muscles. Maridel Fredericksen and her group of researchers at Pennsylvania State University used advanced imaging techniques to look at the cells of infected ants. They discovered that the fungus, which is most prevalent in the head muscles, wraps itself around an ant’s muscle cells and creates networks to coordinate motion.5 These networks direct the ant to a point high enough to spread spores and tell it to lock its mandibles on a leaf until it dies.
There is one type of zombifying organism that affects mammals: toxoplasmosis. About 23% of humans in the United States are affected, but it is more effective at reproducing when it infects mice. This parasitic disease is caused by Toxoplasma gondii, a single-celled organism that takes up residence in its host’s brain. This protist can only reproduce in the digestive system of cats, and it needs a method to get there. This is where mice come in.6 When rodents ingest the organism, it forms cysts in the brain that affect the rodent’s brain chemistry, taking away the normal aversion to feline urine and making the mouse unafraid of cats. The cat is provided with easy access to lunch and consumes the mouse. This deposits the T. gondii in the gut of the cat, where it can reproduce. The organisms then move through the digestive system and are excreted. From there, they mix with soil and the cycle starts over again. Considering the protist causes the rodent to change its behavior, it can be seen as a zombie puppet master. Its control comes from changing the level of certain neurotransmitters, such as dopamine, in the brain. The same organism can inhabit human brains and cause the same changes in neurotransmitter levels. Current research indicates that these changes in neurotransmitters lead to impulsive behavior and may be a trigger for mood disorders and schizophrenia. The brains of people with schizophrenia are three times more likely to contain T. gondii than the general population. One study even suggests the culture of a population with widespread T. gondii infection can be changed by the protist. This is a weak claim at best, but the concept is still interesting.7 It’s tempting to push these theories and suggest T. gondii is responsible for “crazy cat lady syndrome,” but there is little evidence for that, thank goodness. (I have two cats. Just two.) Cat owners are just as likely as those without cats to have toxoplasmosis. Still, cats are complicated pets to own and love, so maybe there is something to this theory. Maybe this is why the internet runs on cats . . . but more likely it’s because cats are cute. Most zombie-causing organisms rarely have much interaction with humans. It’s still good advice to always be careful of zombie organisms, no however interesting you may find them. In the words of the Zombie Research Society, “What you don’t know can eat you.”
Zombie/Wight Rot
The army of the dead was created by the White Walkers with the purpose of taking over the world. As people died in battle or from other causes, the Night King and his lieutenants (aka the Four Horsemen of the Snowpocalypse) could reanimate the corpse and add another foot soldier to their army. But did the process of death and decay stop when they were reanimated? Because the wights are made to fight, yet in almost all cases cannot be killed and can’t heal, they tend to look a little rough after a fight or two. Normal physical attacks don’t have any effect on their ability to stay animated, but what about the bacteria that live on humans and cause decay after death? Would the normal decomposition process be happening while the wights were reanimated? Would it have an effect? It certainly seems from the show that the wights are in various states of injury and decay, but is that based on their state when they died or based on what’s happening to their undead yet moving body? The cause of a wight’s death, the cold temperatures up north, and the humidity all affect how decomposed a wight might be. Even though a wight hand alone has the strength to strangle a man, it’s not going to be as fast or as deadly as a full-bodied wight. Couldn’t the Westerosi just maybe stop dying north of the Wall and wait for nature to take its course?
When a body dies, it goes through several stages of decay (four or five depending on who you talk to), including two chemical processes, autolysis and putrefaction. If you are as much of an NCIS fan as I am, a lot of these terms will sound familiar. I will admit that though I’ve watched more than a few police dramas, reading the details of the decay process was a bit stomach turning. Enjoy!
Autolysis is essentially the body digesting itself. The acidity of cells increases as the CO2 concentration increases. This causes cells to break down and release waste products that eat the cell. The acid in the stomach as well as other enzymes also start to digest the body. Autolysis begins as soon as a body dies. The first, or fresh, stage of decomposition starts immediately after death. In addition to autolysis, the body begins moving toward thermal equilibrium, a process called algor mortis. In addition, rigor mortis, or stiffening of the muscles, occurs due to a chemical change that prevents the muscles from relaxing. Much like Benjen Stark, aka Coldhands, gravity pulls blood to the extremities. There aren’t many physical changes in this stage except maybe some blisters on the skin.
As the body uses its oxygen stores, an anaerobic environment is created—the preferred home of gut bacteria, which now move from digesting food to digesting the body. This process is known as putrefaction. The gas released from putrefaction leads to the second stage, bloat. This is exactly what it sounds like. The gases cause the body to distend as bacteria liquefy its contents. This causes the body to swell. If enough pressure accumulates, the body will rupture, forcing out the frothy liquid. I think this is probably the grossest stage of death.
After bloat, the body enters active decay, which involves the feeding of maggots and more liquefaction of the body through putrefaction. I won’t talk much about insects because there is probably only one species of insect north of the Wall, the chironomid midge, and it isn’t involved in the decay process. If potential wights were further south, however, this is the point where bugs would really get involved. This stage ends when even the maggots have nothing left to feed on. At this point, most body mass is gone and, for those who subscribe to the five-stage model of decomposition, the body enters advanced decay. There’s not a ton left to break down and fewer insects are interested, so decay slows. Many roll this stage into the active decay stage. The final stage is skeletonization. This is exactly what it sounds like. At this point the body is dry and potentially just bones. Decomposition has essentially ended.
There are many factors that affect how a body decomposes: how exposed it is, availability of oxygen, humidity, cause of death, depth of burial and soil type, presence of insects and bacteria, clothing, and, most important to this discussion, temperature. In the case of the army of the dead, they are lucky when it comes to decomposition. The climate is cold, most likely dry, and has very few insects. Since there are effectively no insects involved, the decay would be caused by autolysis and bacteria. Unfortunately—or maybe fortunately, if you are the Night King—bacteria need water to live, and enzymes and bacteria can’t function below a certain temperature threshold. The chemical reactions that cause these processes need energy, in the form of heat, to start and continue. Without heat, they can’t do their job, so the body would be left in pretty good condition. The blood would still pool in the direction of gravity and rigor mortis would still set in; however, the rest of the decay process essentially halts below a certain temperature. Coldhands is a pretty fair representation of a reanimated corpse, though he would have to be strong to overcome the effects of rigor mortis. In cases where someone dies in extremely cold condition, they become mummies instead of decayed corpses. A good example of this are the bodies left on Mount Everest. It is usually not possible to recover the body of a lost climber on Everest in the “death zone” without risking one’s own life. Of the 216 people who have died while trying to summit, only 66 bodies have been recovered. The other 150 have been left to mummify in the cold and dry conditions. In several cases, the bodies trail markers to climbers on their way to the top. George Mallory, whose remains were found 75 years after his death, was virtually free of decomposition. Several other notable bodies are that of Hannelore Schmatz, nicknamed “the German woman,” who died close to Camp IV and remained looking untouched until the wind blew her remains away. One area near the summit is known as the “rainbow valley,” named for the brightly colored, undecayed parkas worn by the corpses on the slope. “Green Boots,” an unidentified climber whose corpse is also in pristine condition, lies in a small cave very close to the summit, right beside the path taken by those attempting to reach the top. What this tells us is that when it comes to the army of the dead, even if you assume a violent death and long exposure to the elements, the wight should actually be less decomposed than it appears—assuming, of course, that it can be reanimated in the first place and that reanimation can overcome rigor. It already has to overcome a whole lot of other biology, so I guess it can also overcome rigor.
Zombie Neurology: What’s Going on in Their Heads?
Until now, I’ve talked about real-life zombies and many examples in nature of one species controlling another. In the case of White Walkers and wights, I hate to say it, but they aren’t real. This hasn’t stopped scientists from asking the question, “But what if they were? What type of disease might they have?” Neuroscientists Timothy Verstynen and Bradley Voytek wrote a whole book about this. I won’t go into too much detail, but I’ll pull out the highlights that might apply to wights specifically. In Do Zombies Dream of Undead Sheep?, the pair investigate the potential cause of traditional zombie diseases with symptoms of lumbering gait, lack of language production and comprehension, anger, inability to feel pain, and hunger for brains.8 They even coined a term for zombie disease: Consciousness-Deficit Hypoactivity Disorder (CDHD). In the case of wights they only exhibit a small subset of CDHD symptoms. They can’t talk, but they are still able to process instructions from a White Walker. They are still very coordinated and are able to move quickly, and they’re pretty deadly with a sword. They are definitely angry and ready to kill, but they aren’t able to feel pain and they don’t seem particularly hungry. Fueled by rage and lacking both the power of speech and the ability to feel pain, their brains—or what’s left of them—are less damaged than those of other zombies. However, there is still some specific damage.
You have probably used the term “lizard brain” or “reptile brain” at some point when referring to an instinctive reaction or impulse. The other day, as I screamed and ran away from a tiny spider, I made a reference to my “lizard brain,” meaning the part of my consciousness operating illogically, on instinct alone—in this case, fueled by my fear of spiders. (In my brain’s defense, no creature needs that many legs. Anything more than four can only be used for evil.) When people talk about their reptile brain, what they are really talking about is the fundamental parts of the brain that are in charge of the things we do on instinct. The amygdala (which is plural, like “data”) are two bundles of nerves behind your temples. These nerve bundles regulate emotions and initiate reactions such as the fight-or-flight response. The hypothalamus, another nerve cluster, regulates functions including sleep, hunger, and response to stressors and also plays a key role in the fight-or-flight response. Verstynen and Voytek theorize that a zombie has an overactive fight-or-flight response with a bias toward the fight instinct. When a human encounters a stressful situation, the amygdala jumps into action. In the case of my spider mishap, my amygdala saw a serious, base-level threat on eight legs headed my way. They triggered my hypothalamus to release a hormone that told my pituitary gland to step up. The pituitary gland released another hormone that told my body to go into stress response mode. With that, my adrenal glands produced adrenaline and set my body on edge, ready to squish the spider or run for the hills. These glands also produce testosterone and cortisol. The result is that my lizard brain—although it is technically a subset of the limbic system—decided that my best chance to live would be to scream like a 5-year-old and flee the scene at a speed I will never reach again. If fleeing wasn’t an option, however, the same hormones would amp up my body to fight. At this point, all higher-level thinking is turned off and I’d be running on pure instinct. Essentially, my amygdala have hijacked my brain and turned me into a deadly spider assassin (or, rather, Usain Bolt).
According to Verstynen and Voytek, the amygdala of zombies are always in control, and the neocortex—the part of the brain that actually likes to think—is on vacation. Zombies, they posit, have adrenaline, testosterone, and cortisol constantly coursing through their veins at very high levels. This amplifies their arousal and heightens their fighting abilities. Generally, the orbitofrontal cortex is in charge of keeping the amygdala in check. It’s needed for higher-level thinking such as strategizing for a battle. Wights and zombies don’t have the ability to coordinate or plan as a group, however, so it wouldn’t be surprising if this part of the brain were missing or severely damaged. If wights had sustained the same type of damage to this region of the brain in addition to their constantly engaged fight-or-flight response, they would exhibit all of the behaviors Jon and the Suicide Squad witnessed in “Beyond the Wall.”
Both wights and zombies are able to understand and respond to sound. Seeing as the wights respond to the noises of humans, they have to be able to hear and process at some level. Their ears, or what’s left of them, as well as their brain stem and primary auditory cortex must be in decent working order. The signals from their ears are relayed through these parts of the brain to determine where a sound is coming from. That is all a zombie or wight would need to be able to act like a zombie. They need only the ability to process that there is a sound and figure out where it’s coming from so they can head in that direction. In most humans, the next stop in language processing is Wernicke’s area. This is where the brain turns the sounds back into language. When this area is disrupted and someone can no longer understand language, it’s called Wernicke’s aphasia. This area may or may not be functioning in wights, but it is definitely out of commission in most zombies. In the case of wights, it’s a little more unclear. Wights listen to their White Walker masters. There has to be some method of communication, even if it hasn’t yet been made clear or if we are supposed to assume it’s magic. Regardless of how a White Walker is “talking” to a wight, there needs to be some function in Wernicke’s area to turn those signals into action. Having a brain that is still intact enough to process commands makes wights stand out from the normal zombie crowd. The complement to Wernicke’s area is the Broca area. This part of the brain is responsible for speech and language output. It turns what the brain wants to say into movements of the mouth and vocal cords to produce coherent language. Neither zombies nor wights have that ability. In fact, the White Walkers aren’t big talkers either. When the Broca area is damaged and language can’t be produced, it’s called, as you can probably guess, Broca’s aphasia. It’s fairly clear that most zombies, all wights, and potentially the White Walkers themselves suffer from Broca’s aphasia. In general, zombies and wights have similar brain damage; however, given their ability to process instructions from White Walkers, it would seem that wights don’t suffer from Wernicke’s aphasia.
Zombie Statistics and a Survival Plan: Can Westeros Get Out Alive?
Zombie outbreaks are quite different from what we observe of White Walkers and wights because zombies typically originate from an infection scenario rather than a puppet master arrangement, but the spread is similar to some degree. Wights kill and the dead are reanimated by the White Walkers to attack the living. From a mathematical modeling point of view, the two outcomes don’t differ much, assuming everyone killed is then reanimated by a White Walker. Given the size of their army, this isn’t a bad assumption to make. The main difference is that killing a White Walker will take out all of the wights he’d created. The zombie spread is similar, but the fight is different. Only a few people in Game of Thrones possess the ability and weaponry to kill a White Walker, so the survival of others north of the Wall is dependent on the same skills as surviving a more traditional infectious disease model. Luckily, many professors and grad students with access to fast computers like to do such things in their spare time. There are 37 papers about zombies on arxiv.org, the academic preprint server. One in particular, published in 2015, is the most comprehensive statistical analysis of the potential spread of zombieism. It is fairly general and can be easily modified to fit the wights of Game of Thrones. Alexander Alemi and his colleagues at Cornell University started with a traditional disease spread model, the “Susceptible–Infected–Recovered” (SIR) model, and generalized it to the SZR model, “Susceptible–Zombie–Removed,” where “removed” means a zombie has been killed (for good).9 This model looks at the change over time in these three populations based on parameters set at the start. The kill parameter gives the probability that a human kills a zombie, and the bite parameter indicates how likely it is that a zombie will bite a human, thereby infecting them. In the case of the wights and White Walkers, it’s not the bite that changes a human, it’s the kill. When looking at how this model applies to Game of Thrones, the bite parameter can be easily changed to the wight parameter. (It even rhymes!) Alemi’s paper deals directly with zombie outbreaks in different sized populations. Considering that wights had small populations to work with until the end of season 7, this makes the paper’s model applicable. They used a simulation that models one-on-one interactions between zombies and humans, using probabilities of bites (or wights) and kills (of wights by humans). They found that the probability of stopping a zombie outbreak is directly proportional to the ratio between a human’s ability to kill a zombie and a zombie’s ability to kill a human: kill/wight. If that ratio is 1:1, meaning they are equally likely to kill each other, humans will always stop the apocalypse. Their model showed that one side will always win: either humans kill all the zombies, or the zombies turn all the humans. As the war rages, either everyone will be turned, or all zombies (or wights) will be killed; however, the results were somewhat dependent on population. If there are more than 100 people, they are as likely to survive as 100,000 people. If there are fewer than 100 people, however, there is some fluctuation, and if there are fewer than 10 people, no one’s getting out alive in most cases. These cases all involve only one zombie thrown into a population of humans. These cases were applicable when the Night King was first created or if a wight were to infiltrate a wildling camp. Let it be said that in the current state of affairs in Westeros, we are well past that point.
This model only gives the outcome for an evenly distributed population in which a single initial zombie can interact with any other person. This is also not the case in the North. The population north of the Wall is not evenly distributed but clustered in groups of travelers, be they wildlings or ranging parties. Alemi’s team modeled this scenario as well by creating a grid with one person per box and dropping one zombie in the mix. It can only turn neighbors, and its success rate is governed by the same kill/wight ratio from the first model. What they found was that zombieism spread in a network. All isn’t doom and gloom, however—the good news here is that there are pockets of survivors. There is a critical threshold of interactions that lead to bites, under which the apocalypse is halted but over which everyone is doomed. If humans are slightly less than half as good at killing zombies as zombies are at killing humans, humans will stop the spread of zombieism. Again, this is all assuming one zombie and a population limited to interactions with neighbors. The final map of infection leads to a fractal pattern. This isn’t really relevant to Westeros but is interesting nonetheless. From this initial model, we can then move to a more realistic model of a population that is spread out in clusters, as seen in the United States. In this model, zombies were also given the ability to move, however slowly. Humans were not given the ability to move, under the assumption that mass hysteria would lead to road closings. (I’d say that’s a fair assumption.) They assumed one zombie for every million people. What they found was that most of the US population became zombies within a week and the spread depended largely on population density. Remote areas resisted the fall into zombieism well past the four-month mark. After running their simulation a number of times with different starting points, they created a zombie susceptibility map. If there is a zombie outbreak, you should definitely avoid major cities, but more importantly, you should avoid the connections between cities; the pathways between cities can be affected by either city, so you are more likely to be attacked in those areas.
What does this mean for Jon, the wildlings, and really, at this point, the rest of Westeros? It’s hard to say exactly, but I think they are pretty much screwed. The key difference between the zombie model presented here and the army of the dead is that there are nodes—that is, White Walkers—that can negate the entire model. According to Dany, there are roughly 1,000 White Walkers. If we assume some of the Westerosi—that is, an army armed with dragonglass and Valyrian steel that is evenly matched with Walkers—are able to kill White Walkers, half the army would be lost in each direct battle with a Walker. It would take an army of 2,000 evenly matched and armed soldiers to have a statistically probable chance of killing the Walkers. That, of course, assumes they can fight through the wights to battle the Walkers. Dany also estimated there are about 100,000 wights, so each dragonglass-armed soldier must kill 100 wights to then have a 50% chance of killing a Walker. Meanwhile, the zombie plague has spread across nearly the entire continent in a week or so, stopping Jon and Dany from recruiting the needed soldiers and adding to the opposing force of wights. So, the odds are amplified against our heroes as the battle progresses. At this point, if you are a random resident of Westeros, do what you would do anyway: get off the road, get out of the city, find somewhere with fresh water and food, and just try to wait it out. Really, though, there’s not much hope for you barring the deus ex machina of Drogon (and we saw how that went in season 7).
Zombies so often are used as a dramatic tool to bring out the true nature of each main character. In Night of the Living Dead, the true horror was the collapse of the group trying to survive, and the zombies served to push the collective to self-destruct. In Max Brooks’s World War Z, the story uses a zombie apocalypse to provide commentary on the modern geopolitical landscape. In Game of Thrones, the army of the dead serves as a monster MacGuffin to reinforce exactly how altruistic or short-sighted (or both) our human characters are. In that way, although the rules are different and the statistics may not apply in the same way, the army of the dead serves as a dramatic vehicle driving the story, just as zombies do.
Bonus: Zombie Dragons
As discussed in chapter 3, the season 7 episode “Beyond the Wall” left a number of unanswered questions. I addressed some of them but saved one of the big questions for this chapter: How did the wights pull zombie Viserion out of a lake, and where did those chains come from? We need to make a few estimates to get to the answer. First, how long would it take for the ice to freeze solid enough to hold a dragon? Second, how long does it take to forge or find and attach chains to Viserion? Third, how strong would the army of the dead need to be to make this happen, and how would they be able to pull hard enough without slipping on the ice? As for how thick the ice needs to be to hold a dragon, there’s a pretty straightforward equation for that. The required thickness of the ice is dependent on the square root of the dragon’s weight. (Technically, this equation was derived for planes . . . but same thing, really.)10
,
where S is the thickness of ice needed in inches, C is a constant that depends on the type of ice—either sea ice, river ice, or lake ice—and W is the weight of the plane (or dragon) in tons. This formula works only for ice created at about 16°F; for higher temperatures, S will be about 25% thicker. Since Viserion fell in a lake, C = 3.75. Assuming Viserion is about the weight of a Boeing 747 in tons, W = 200 tons. These values indicate that 4–5 feet of ice would be needed. At about 20°F the lake would freeze about 1 inch per day.11 This would give the White Walkers about two months to procure an insane amount of chain. Luckily, due to the conditions, Viserion wouldn’t have decayed much by then.
As for the chains, if you type “where did the Night King” into Google, the second suggestion, after “. . . come from?” is “. . . get those chains?” Clearly this is something everyone wants to know. Some have suggested they are of giant origin. This would certainly explain how they were forged, since I don’t think wights like forges. There’s no great scientific explanation for how creatures that clearly can’t swim found and attached giant chains to a dragon in a lake, so I’m going to leave that as an exercise for the reader. However, some have asked how a 200-ton dragon could be pulled out of a lake without ripping his wings off. This is a valid question; that amount of stress is really too much for most joints to handle. As I’ll elaborate further in chapter 7, however, dragons most likely have extra-strong bones, which would counteract the wing-ripping problem. (Turns out it doesn’t really matter.)
As for how strong a wight has to be to pull those chains, the first thing we need to know is how heavy Viserion would be when submerged in water if buoyancy is considered. I’ve assumed Viserion weighs about 200 tons, or 400,000 pounds, so the downward force is ~400,000 pounds. Buoyancy would hold him up a bit and is given by the equation
where ρ is the density of water and V is Viserion’s volume. Assuming again that he’s roughly the weight of a 747, his volume is about 876 m3. This equation gives a surprising answer: if fully submerged, Viserion would be subject to a buoyant force of about 2 million pounds. This is five times his weight. He would float! Guess that answers the question of how the wights swam down to attach the chains.
The question, then, is how hard the wights would have to work to drag Viserion close enough for the Night King to reanimate him. In reality, this isn’t much of a problem, either. He was already above the water, so the Night King could have touched his snout without much need for pulling anything besides his head. If Weiss and Benioff had simply paid attention in physics class, none of these pesky plot holes that the internet forums can’t stop talking about would even exist.