Vampires are one of the most popular horror figures in human history. They feature in popular literature over and over again, spanning from like of the O.G. bad boy Dracula, to the sparkling mess that was Edward Cullen and his family. Despite the many variations of vampire out there, they usually follow some pretty standard rules:

• They can’t go in the sunlight, either because they’ll die, or because they’ll look really silly (re. the Cullen family) doing it.
• They drink blood to survive (this can either be human or if they’re a bit soft, animal). The frequencies in which they need to drink blood varies from tale to tale, but let’s assume it’s around every month that they need to feed.
• The people that they bite either die or become vampires themselves.

Now this leaves us with an interesting question: if a vampire bites one person every month, how many vampires would there be by now?

Well,  let’s pretend and say that the very first vampire was created (or is it born? Whatever, I’m not a vampire scientist) at the turn of the 19^th century. He’s kind of lonely and very hungry, so he bites a poor, unsuspecting villager on the neck. As he wants a friend, and has good self-control, he doesn’t kill his victim. Instead, he turns the villager into a living dead pal. So that’s two vamps now. Come next month, those two vampires get hungry and feed off two more villagers and all of a sudden you’ve got 4 vampires. The next month after that at feeding time those four vampires turn into eight. You can see where this is going.  By the end of the first year alone you have 2048 vampires.

Currently, there are just under 7.5 billion people on Earth. By month 34, if this trend continued at a consistent rate, you should have 8.6 billion vampires. Given that that’s over a billion more than the current population, let alone the population of the 19^th century (which is estimated to be less than a billion) you can see where the problem with vampires comes from. This means by extension (although is always very sketchy practice to assume things based on one calculation) we’re either all vampires (tell that to my sun tan) or that they simply don’t exist.

There are some holes in this calculation. It assumes that vampires feed on humans only once a month. However, some stories have them feeding up to once a night, meaning it would be all over for humans even quicker. It also assumes that vampires turn their victims rather than just killing them every time. This also doesn’t factor in the potential for a Buffy-eques heroine to save the day by keeping vampire populations to a sustainable limit. Maybe there are a small group of very controlled and thoughtful vampires somewhere that just eat animals and hold hands and sing Kumbaya, but I doubt it. Believe what you want to believe, but when in doubt, always make sure you do the math.

Credit where credit is due, this guy managed to do the math first. Doctor Karl also covers it in his fantastic new book, The Doctor. If you’re looking for something to add to your Christmas list, I couldn’t recommend this enough.