Monday, April 27, 2009

Simulating Humanity's Post-Zombpocalypse Fate

The above picture is taken from an old project of mine. The goal was to build a simulative model in order to predict what humanity's fate would be, long-term, in the event of a zombie apocalypse as seen in classic films like those of George Romero. It was actually my final project in a high school class that was based around using a computer program called STELLA to model these sorts of complex situations. Prior assignments had modeled things like the spread of a disease and the populations of wolves and deer in a wildlife preserve; part of my interest in putting together this particular simulation came from how it mixed elements of those two prior models. You have predators which infect and convert their prey. How would such a premise logically play out?

The simulation takes into account more factors than just the method by which the virus spreads. The two major things I wanted to take into account beyond the basic model were supplies available for salvage and survivor's experience in dealing with zombies. If there's a ton of abandoned houses around with fully stocked fridges, an average survivor has lower odds of starving or freezing to death. If a person has never had a first-hand encounter with a zombie before- knows nothing about the situation they're in except that there's a moving corpse in front of them- then their odds of surviving that encounter are going to be alot lower.

The variable in my simulation, then, was the size of the initial outbreak. If the dead rise from their graves all over the world, and society has collapsed by the end of the week, people are going to be less prepared than if they've had a couple weeks to watch news of nations in other hemispheres slowly crumbling while wondering if they'll be next.


The model's results are interesting to me in three different ways:
-The single scariest factor is a way in which the zombie-human factor does *not* match the typical predator-prey relationship. Cruel as it is, that type of system has inherent balances; wolves will start starving to death if they kill and eat 90% of the deer population. But zombies don't starve. They get along just fine even when there's only one of us left for every ten of them.
-As you can see, the variable- the size of the initial outbreak- leads to some interesting variations in the model. But even the smallest outbreak- only 50 initial infections- still leads to the death of over 80% of the population. However, the only scenario in which humanity is actually wiped out- leaving only a population of slowly eroding zombies- is the one where a full quarter of the population is initially infected and turned, so that when only the seasoned veterans remain there's just too many zombies left for them to handle.
-Lastly, the model ignores/handwaves a certain factor which is rarely addressed in zombie fiction (Though Max Brooks made a concerted justification effort in World War Z, bless his heart): There is NO WAY the virus is going to spread effectively if it's only transmitted from a zombie to a living person's bodily fluids. Because the world's just too big. In zombie fiction you can drop into some random point in the wilderness and there'll be a hundred zombies in a mile radius. The virus will spread across the country like wildfire. But in practice. . .how does a zombie make its way across open countryside to another major population center? Romero's zombie virus, as presented, just isn't cut out for global armageddon.


Anonymous said...

Good point on that last part about bodily fluids and the difficulty with which the virus would spread over whole continents like that.
Another seldom addressed point is that zombies aren't, from a military viewpoint, all that scary in the end. Sure, there might be lot and they might be tough, but they're in essence a slow enemy without any tactics or intelligence that requires close combat to infect anything. Against a modern force with training, good equipment, tactics and discipline. I have hard time imagining any modern, disciplined military force would be overwhelmed by a zombie invasion if they had even a day's warning. And given the speed with which the zombies would most probably spread, they have that time. And that's just the infantry. Throw in the tanks, helicopters, air support and other goodies, and it'll be nothing but a gruesome, nasty skirmish.

Unless the whole world got infected at the same time or something. Factoring in even possible stress, confusion and fear, it's unlikely at best that a properly trained army regiment would fail to carry out a zombie extermination if instructed even on a basic level.

Cooked Auto said...

Regarding military combat I have to say Brooks handles that rather well during the Yonkers chapter in WWZ, as he takes a lot of factors into account.
Firstly we have the sudden change in combat doctrine, hitting a head is a lot harder than hitting a torso, especially during a stressful situation. That and it goes against what most modern armies train in and would require additional training. Also the fact that a zombie can not be taken down unless it is a head shot affects the situation as it's often better to wound an enemy as it then requires two additional soldiers to move the wounded away from the battle, further sapping the enemies fighting strength. Which is not the case with Zombies.
Secondly the political climate that is occurring during the books time line also influences. That and the lack of general knowledge of the enemy their facing due to people ignoring the ever growing threat despite warnings. Which was a rather big theme in the buildup before the collapse.

Also the fact that overkill doesn't really work against an enemy that can only be destroyed with a headshot. Of course they manage to cause casualties on the horde but they also had numbers on their side as well since Yonkers horde is made up of large parts of the population of New York. As it became rather clear, ammunition only lasts for so long. And as Brooks points out in several places during the Yonkers chapter is that certain things that works on humans when it comes to weapons doesn't work on zombies.
But you do have a point in that a properly trained army can defeat a zombie horde very easily, but at the same time it essentially means retraining the troops to face an entirely new foe.

But I do agree that most zombie scenarios seem to hand wave the whole factor of how the virus actually spreads. Brooks is also very cloudy in the subject even in the Zombie Survival Guide with only making elusive mentions that the Zombies may possess a seventh sense of sorts to able to find humans or any living organism to devour.
Although it's interesting to see how Brooks takes into account today's global travel when it comes to spreading the virus globally, alongside peoples ignorance about the subject. It doesn't explain everything though, especially towards the end when the human population decreases into the various zones but it works quite well in the beginning.

Dagda said...

I think what hamstrings the military in your average zombie apocalypse isn't the zombies themselves- in a straight fight 1 zombie is a pushover for an adult civilian who knows what they're up against- but the question of logistics. How long the military can operate at full capacity when throughout the home front people are abandoning the infrastructure that provides them with food, fuel, power and many of their means of communication.

Note that this simulation didn't allow for the possibility of containment. You might assume that the virus was released in a such way that the first zombies weren't all located in a single area.