You and Me and Toxoplasma Gondii.

I lived with a cat for about 5 years.  In that time, I cleaned his litterbox, slept with him at the foot of our bed, watched TV or played video games with him in my lap, and all the other standard cat-owner behaviors.  Never once did I suspect that a mind-controlling brain parasite might have lodged itself in my blood stream and been changing the course of my life in secret.

We, as humans, like to consider ourselves the masters of our own fates.  We imagine that we have the sacred power of free will, when it seems in truth that we constantly butt up against genetic predisposition, social structure, and our birthplace when we "self-determine."  But what if there was something more subtle at work, shaping our movements and changing the course of human history with an invisible hand?  No, not the Illuminati or some kind of Cthulhu cult.  A simple parasite.

"I Poop Mind-Control."

Toxoplasma gondii. This single-celled organism thrives in cats, where it produces eggs that are eventually expelled by the cat.  All sorts of animals can then become carriers for T. Gondii (which is my new hip-hop alias, by the way) if they come into contact with feline fecal matter containing the eggs. T. gondii forms cysts throughout its new host's body and brain. Fascinating, tho, is that despite this parasitical infection, the new hosts are often perfectly healthy.  In fact, infected rats are practically indistinguishable from non-infected rats, with one exception:  They are less afraid of cats.

Genius Risk Assessment.

Such a major departure from normal rat logic, i.e. "Cats are going to eat me and then I'm dead" bears further attention.  Evolutionarily, it makes perfect sense- parasites that move back into cats are more likely to begin their cycle over, and thus, more likely to reproduce.  Rats that get eaten bring the parasite back to it's original proginator- a sort of exodus back to the motherland (cat intestines) by a new generation (of disgusting parasites).  There, the wonderful (horrible) cycle of life begins again- all because the rats displayed a tremendous lack of self-preservation instincts.

Here's where it gets good- Humans can carry the parasite in the same way that rats due, and are often infected from handling soil or kitty litter.  For the most part, the parasite is unlikely to make us ill, and it's even more unlikely that it will complete it's journey back into a cat (since even the most aggressive housecats don't usually eat humans) but that doesn't exclude the possibility that it could have an effect on human behavior.  Parasitologist Jaroslav Flegr of Charles University in Prague gave psychological surveys to both people infected with Toxoplasma and uninfected control groups. The Infected (I like how this sounds more and more like a horror movie) showed a small but statistically significant tendency to be guilt ridden and insecure. Strangely, on average. Infected women tended to be more intelligent, outgoing and friendly, and sexually active.  Infected men were more likely to be jealous or suspicious, and more aggressive.  Okay, that's sort of weird, but it shouldn't really have that big of an effect on us, right?  Kevin D. Lafferty found in 2006 that T. Gondii infection is extremely common and rates can vary greatly from country to country; 7% of Brits carry the parasite, but about 67% of Brazilians were carriers.

This, but with more cats and sex.

Before you run off and create the next blockbuster sci-fi thriller (I'm looking at you, Michael Bay) or start suspecting your crazy cat loving aunt is a servitor of mind controlling parasites, the data isn't really strong enough to do anything more than suggest there's a correlation.  It's a pretty enticing concept, I have to admit.  What if that girl you like is only nice to you because she has a cat and IS ONE OF THE INFECTED.  Would the parasite eventually evolve so that we would desire to have MORE CATS and also maybe, you know, LET THEM EAT US?  Slowly but surely the infection spreads around the world and then WOMEN ARE FRIENDLIER and MEN ARE MORE SUSPICIOUS and RATS ARE HANGING OUT WITH CATS and EVERYTHING IS IN BOLD CAPITAL LETTERS EXPLOSION EXPLOSION EXPLOSION!

It's fun to hypothesize.