How Long Could Humanity Survive a Zombie Apocalypse?

An academic paper suggested just 273 humans would remain 100 days after a zombie apocalypse. GoodLifeStudio/Getty Images

The threat of zombie apocalypse has been calculated by way of a research assignment your university wasn't cool enough to give you. Physics students at the University of Leicester in England recently published actual studies on how a zombie apocalypse would affect the human population, and how long it would be before everyone reverts from simply running in terror to mumbling, "brains, brains, brains." Results were published in the school's peer-reviewed undergraduate publication, Journal of Physics Special Topics. Special topics, indeed.

As the first of two studies showed, most of us when faced with a viral zombie epidemic would wind up kissing our humanity goodbye, with a scant 273 survivors worldwide compared with millions of zombies after only 100 days. The students assumed each zombie could find one person per day and had a 90 percent chance of infecting its victim.

The students calculated the sobering findings by using an SIR model, an epidemiological model used to describe the spread of disease in a population. Three categories of people/zombies are accounted for by the program: susceptible (those who are still at risk of becoming infected), the infected, and the dead/recovered. (SIR is short for susceptible, infected and recovered.)

The initial study assumed humans as helpless, but a follow-up gave us some added moxie. The subsequent study applied new parameters, like humans making new babies and learning how to fend off or kill zombies, to the SIR model. "Interestingly we find that it is actually possible for our population to survive the zombie epidemic under these conditions. It can also be seen that once the zombie population has been wiped out at roughly 103 days [1,000 days or about three years], the population starts to recover at 104  days [10,000 days or about 27 years]," the researchers write.

The whole point of papers like these is to let "the students show off their creative side and apply some of physics they know to the weird, the wonderful, or the everyday," said Leicester physics professor Mervyn Roy in a press release. But some people  take the zombie apocalypse scenario a little more seriously.

Gunnard Engebreth and his Madison, Wisconsin-area friends are determined to be part of the re-emergence of humanity, having already developed a plan and assigned supplies and responsibilities. They devised this at Mickey's, a local watering hole, which will be the site of their defense.

"When the zombie apocalypse hits here is our plan: Grab your backpack with any tools, food, clothes that fit. I am also tasked with bringing my solar panels and electrical devices to begin setting up redundant power options," he explains in an email. Using a nearby canal, they'll set up a small hydroelectric power station, after fortifying the premises from unwanted brain-eating intruders. They've also figured out ways to grow crops on the property, purify water and communicate with scavenging parties as they roam the area looking for supplies.

So far, the SIR model hasn't been employed to figure out what will happen when Engebreth's clan faces a true crisis before the zombies are eradicated: they run out of beer. Perhaps a third study is warranted?