This is a natural thing.
Zombies ... what if I told you that they're everywhere?
Hold on to your brains. Here's the story:
You know about your run-of-the-mill parasite — where one insect lays an egg inside another, and when the larvae hatches, it consumes its host from the inside out until it's ready to emerge and take over the world?
It seems that many parasites take things a step further:
These kinds of parasites bend their victims' wills to serve a new master.
The horsehair worm grows up inside a cricket and then drives it to commit suicide by drowning.
The horsehair worm needs water in order to reproduce. When it's old enough to mate, the parasite releases proteins that cause the crickets to become suicidal in a very specific way: by drowning. A host cricket finds water and flings itself in. While it drowns, the horsehair worm wriggles its way out, free to hit the singles scene.
And this isn't an isolated thing either. One scientist in Japan found that in one stream, deviant suicidal crickets made up 60% of the diet of local trout!
Then there's this "head-banging zombie caterpillar" brainwashed by wasps.
After being stung by a parasitic wasp, this caterpillar becomes a body guard: Here it is beating off a curious weevil to protect the cocoons of the very insect that is devouring it from inside. So, in a way, the caterpillar and cricket are no longer their original selves.
It's like the cricket and the caterpillar have become extensions of the minds of their parasitic conquerors...
Parasites even control group behavior. Tapeworm-infected sea monkeys turn bright red and swim together in clumps.
Why? So they can be more easily spotted and eaten by flamingos, which — you guessed it — is exactly where those tapeworms like to breed.
You want to take solace that this is just a thing of the creepy insect world, right?
A parasite called "toxo" has crossed the arthopod-mammal barrier without a problem.
"Toxo" is a one-celled parasite that lives in rats but needs to be inside cats to reproduce. And yes, this is why people are advised to avoid changing litter boxes while they're pregnant.
See, in rats, this toxo manipulates their brains in a way that makes them think it's a smart idea to run toward the smell of cat pee instead of away from it, making the rats easier for cats to hunt.
But if a pregnant person encounters a toxo while cleaning out the litter box of an infected cat, it can cause serious birth defects to the fetus.
It's just not natural!
Except — it is.
It turns out that 1 in 3 of us humans actually have this toxo in our own brains.
Scientists are very divided over whether the parasite is actually manipulating human behavior. Some think they see it in personality tests, car accidents, and schizophrenia.