We're all just one impulsive Google images search away from facing the unblinking darkness that lurks within the heart of man. But that black pit of twisted evil and decay shouldn't surprise anybody; it's rooted in our genetic makeup. Literally.

6 Ancient Diseases

Continue Reading Below Advertisement

Back in biology class, you were probably taught that DNA was a sensible, organized system. When they called it "the building blocks of life," you probably pictured DNA as a series of neatly edged Legos snapping together to form a cohesive whole. When in reality, DNA is more like an old scrapbook that someone has torn up, pasted back together, filled with old newspaper clippings about murder and then taken into the bathroom with them.

Photos.com

She knows what she did.

Continue Reading Below Advertisement

A large part of this internal mess comes from the endogenous retrovirus. A normal virus works by moving into a host cell and using it to reproduce, but retroviruses reproduce by actually mixing their own genetic material with the DNA of the host cell they're invading. If a normal virus is a home invasion robber, busting down your door and smashing up your stuff, a retrovirus is the creature from Alien, impregnating you with its horrible seed and producing a twisted mockery of everything you once were, and then laughing as that atrocity murders all of your friends. Metaphorically speaking, of course.

Continue Reading Below Advertisement

In the distant past, retroviruses picked up by our ancestors would occasionally find their way into the sex organs, and the newly virused-up DNA was passed along to their children. As a result of all this virus-laden boning, we modern humans have about 100,000 of these microscopic gate-crashers cluttering up our DNA. When you add in the assorted genetic trash they've left behind, more than 40 percent of human DNA is made up of ancient, sinister and almost certainly cursed viruses.