Where do our thoughts, moods and urges come from? Do they originate in our minds? We like to think so. The idea of free will, that we are in control of our behavior and indeed our destinies, is a powerful cornerstone of what we feel makes us human. However, how much of that free will is real and how much is illusion? Are we truly in control of what we think and do? Throughout the natural world we can see examples of instances in which creatures have been taken over by other organisms, their minds enslaved or manipulated to do the bidding of their invaders. Is it possible for the same thing to happen with us; for our free will to be corrupted by violating outside forces? Even more pressing, is it possible for our humanity to be completely altered by such forces? As we shall see, we may not always be as in control of who we are, what we think, and how we feel, as we’d like to believe.
The effects of various microscopic organisms on the animal kingdom have been well documented, and range from subtle, mild alterations or behavioral tweaks to full blown zombification and mind control like something from a horror movie. There are numerous examples of both parasites and viruses manipulating the behavior of their animal hosts, either to gain some advantage or benefit, such as passing itself on to a new host or moving on to the next stage of their often complex life cycles, or in other cases as merely a byproduct of infestation which confers no obvious advantage on the intruding organism.
Many parasites exhibit extremely intricate lifecycles, which require that they be passed on to hosts of completely different, disparate species that may not even share the same habitats on their complex journey to their “definitive host,” which is the end of the line, the final stage, where the parasite will finally reproduce and die. In order to move on from one intermediate host to another, it is often necessary to tweak or transform the host’s behavior to facilitate the process. The most well-known example of this can be seen with the malaria parasite plasmodium, which at first makes its mosquito host become more cautious and less likely to bite in order to keep it safe as the parasites develop in their gut. After it has reached a certain stage of development, the parasite sends its mosquito host into a furious biting frenzy, compelling it to bite far more frequently and for longer periods of time than usual in order to spread itself as much as possible.
Another classic example of this is the lancet liver fluke, Dicrocoelium dendriticum, which is typically found in the livers of grazing mammals such as sheep or cattle. The first intermediate host is land roving mollusks, such as slugs or snails, the slime trails of which leave behind the parasite, which are then ingested by ants. The next step is for the parasite is to make it into an animal such as a cow, but how to get there? In short, zombification. The parasitic larvae make their way to the ant’s brain, where they encyst and create a strong urge for the ant to climb to the highest blade of grass it can find at night. Upon reaching the top, the cysts cause an involuntary spasm of the mandibles of these “zombie ants” through the release of tetanus, which causes the ant to bite down hard on the grass and prevents it from going anywhere. In the morning, a grazing mammal comes along, eats the grass with the immobile ant on it, and the lifecycle is completed.
Other examples of such host manipulation can be found with thorny-headed worms, which alter the neurotransmitters of their hosts’ brains to achieve the desired result of moving on to birds from its initial host, a type of crustacean known as a gammarid. These gammarids typically live in ponds, and their natural reaction to surface movement or disturbances is to seek darkness and to dive into hiding beneath mud on the bottom. However, when infected with thorny-headed worms, they instead swim up towards light when there is a disturbance at the surface, where they are eaten by birds and therefore complete the parasite’s lifecycle. The worms achieve this by producing a strong immune system response that releases large amounts of the neurotransmitter serotonin, which then disrupts signals from the eyes to the brain and likely tricks the gammarids into confusing up for down and light for dark.
A particularly gruesome example of changing host behavior can be seen with a type of parasitic worm known as hairworms, which can only reproduce in the water. The hairworm of the species Spinochordodes tellinii uses a species of grasshopper as its host, after which its goal is to get into the water to mate. To do this, the hairworms generate proteins that corrupt the grasshopper’s central nervous system and compel it to seek out the nearest body of water and dive into it. Upon hitting the water, adult parasitic worms burst forth spectacularly from the host into the water, dramatically and horrifically killing the host and dispersing into the new habitat to mate and reproduce.
This sort of host manipulation can be extraordinarily complex. In the case of one nematode which infects tropical canopy ants, not only is the behavior of the host altered, but its actual physical appearance as well. Once invaded by the nematode, the normally black ants display abdomens that become unusually bulbous and bright red. Additionally, nerve damage caused by the nematodes instils within the infected ants a compulsion to constantly raise their abdomens in the air, the total effect of which is to make the ant look like a nice, juicy, inviting berry, after which they are picked off by the nematode’s final host, frugivorous (fruit eating) birds.
There are several types of parasitoid wasps that also manipulate their hosts in shockingly sophisticated ways. Parasitoid wasps typically lay their eggs in a host, after which the larvae will eventually hatch and feed upon it. One type of wasp native to the rainforests of Costa Rica targets the species of spider Anelosimus octavius as its host. This type of spider generally weaves knotted, gnarled webs of haphazard threads, but infected individuals will go off and spin webs that are completely different in design. Infected spiders essentially have their brains hijacked into weaving webs that have a platform covered by sheets of webbing that protect it from the rain and elements, as well as an odd opening at the end of the platform. When these bizarre webs are finished, the wasp larvae emerges from the spider, killing it, makes its way to the end of the well protected platform, and hangs from a cocoon through the opening that the spider has graciously provided. It is extraordinarily creepy that this parasite can not only alter its host’s behavior, but also essentially have it act as its own personal architect.
The parasitoid wasp, Glyptapanteles, also demonstrates a particularly dastardly form of mind control on its host, actually turning it into a guardian for its larvae. The wasp first lays its eggs within its host, a caterpillar of the moth species Thyrinteina leucocerae, after which they will develop until they are ready to pupate. This is where the weirdness begins. The larvae exit the host peacefully and create cocoons nearby, while the still living caterpillar starts to exhibit highly unusual behavior. The caterpillar stops feeding and ceases all movement, only springing to action when an intruder draws near, when it will suddenly vigorously thrash its head back and forth. This is done at the slightest provocation or disturbance, and serves to discourage any potential predators from feeding on the pupating wasp larvae, essentially serving as their own personal bodyguard until they emerge from their cocoons, after which the caterpillar dies.
Parasites are not the only organisms that have the ability to control the minds of their hosts, and there are even viruses that play the role of evil puppet masters. A type of virus called baculoviruses is known to change the behavior of hosts to suit their needs as well. One form of baculovirus infects caterpillars, invading the cells and causing them to produce so many new viruses in the hosts that they visibly swell up. After this, the caterpillar is gripped with an irresistible compulsion to climb up to the tops of plants, after which the virus releases an enzyme that causes the host to literally disintegrate, raining the viruses down on the surroundings where they will infect new hosts. These baculoviruses are apparently scattered all over the place, including crops for human consumption, with some everyday vegetables we eat shown to hold staggering numbers of them. Fortunately, they are harmless to humans.
It is obvious that there are a plethora of parasites and microorganisms that have the capability to dramatically manipulate the behavior of insects, but what about humans? Is there any such organism that exerts its mind control upon us? It is little understood to just what extent we are influenced by such organisms, as we have much more complicated nervous systems made up of far more neurons than the insects that have been studied so far, making it difficult to ascertain just what sort of mind altering effect may be evident in us. Nevertheless, there are certain cases that we do know of where microorganisms have shown to exert an often dramatic influence on our behavior.
Perhaps the best known example is that of the rabies virus, a highly virulent and deadly disease that infects a wide range of hosts and is spread through bodily fluids such as saliva, typically in the form of bites from infected animals. The rabies virus does not have a complex lifecycle and is fairly indiscriminate in which hosts it infects, instead incurring a fitness advantage simply by spreading itself as far and wide as possible. Upon infection, the host exhibits a wide range of symptoms as the disease acts upon the central nervous system, including anxiety, restlessness, confusion, hallucinations, paralysis, involuntary muscular contractions, uncontrolled perspiration, salivation, and pupil dilation, and hydrophobia (fear of water), which usually make themselves known after an incubation period of around 10 days.
The most dramatic symptom of rabies is a marked increase in agitation, anger, and aggression, a trait that makes infected animals more likely to bite and thus increase transmission of the virus. Within a period of mere days after exhibiting symptoms, the victim will fall into a coma and die if not treated. Although mostly found in animals, it is possible for a human to contract the disease through a bite from an infected animal, and if it is not treated in a timely manner they will invariably show all of the same symptoms, including the heightened anger and aggression, although our acute self-awareness allows us to somewhat control our urges to lash out and bite everything that comes near us, and there has never been any confirmed case of human to human transmission of rabies as of yet.
Many may already know about the effects of rabies on the human nervous system, but there is another, more bizarre microorganism that can have a profound effect on our behavior as well. Toxoplasma gondii is a microscopic parasite that reproduces in the guts of cats and is evicted through their feces. Small mammals such as rodents, as well as birds, can contract the parasite after which they are eaten by cats to complete the lifecycle. The parasite invades the central nervous system and forms cysts, which influence the behavior of the host in some rather bizarre ways. In rats, it deprives them of their natural fear of the smell of cats, and creates disorientation, making them less cautious and more likely to run around out in the open or even approach predators, where they will be eaten by the final host. They also show a general increase in activity and restlessness, making them attractive targets for cats. The parasite also generates extra testosterone in male rats, making them more attractive to mates and allowing them to spread the parasite through sexual contact, as well as further reducing fear and increasing boldness.
Although humans are not a natural host for Toxoplasma gondii, and we are essentially a dead end for the parasite, we nevertheless can contract it from handling cat litter or feces that have been exposed to infected animals, or ingesting raw or contaminated food. In the case of human infection, the parasite also is believed to alter our behavior in various ways. The physical symptoms of human Toxoplasma gondii infection in healthy individuals are slight; usually only mild, flu-like symptoms, but the parasite forms cysts in the brain which recent studies are finding can manipulate our behavior even in the absence of physical symptoms. Interestingly, these behavioral modifications are different depending on whether the host is a man or a woman. For men, Toxoplasma gondii infection has been shown to make them more introverted, jealous, morose, suspicious, and oblivious to others’ opinions of them, as well as generally more anti-social and likely to break rules. Infected women, on the other hand, have been shown to exhibit the exact opposite, becoming more outgoing, friendly, trusting, self-conscious, concerned with appearance, and law abiding, as well as more promiscuous. Both men and women who have been infected with Toxoplasma gondii have been shown to have impaired motor skills, and show more inclination to take risks than non-infected people, a fact which makes them 2.6 times more likely to be involved in traffic accidents. Various researches has also linked Toxoplasma gondii to a higher rate of schizophrenia.
It is not known exactly how the parasite performs this subtle reprogramming, or if it serves some purpose in human hosts or is merely a side-effect of infestation. Typically the parasite is not dangerous to humans except for pregnant women and people with weakened immune systems, in which it can cause serious health complications such as seizures, mental retardation, deafness, blindness, intracranial calcifications, and death. Somewhat ominous is the fact that it is believed that around 1/3 of the world’s population is infected with Toxoplasma gondii, and around 60 million U.S. citizens are thought to be carrying it. It is certainly enough to incite speculation of what sort of subtle effects this microorganism may be exerting on society as we know it.
Recent research has uncovered yet another microorganism that may influence human moods and behavior as well; the microbes living in our guts. Human beings, indeed all animals, have a vast number of various types of microbes living in our stomachs and digestive tracts. It has been found that a person’s brain connections, essentially how we are wired, seem to show a correlation with the type of microbe most prevalent in an individual’s digestive system, which is believed may have an influence on our moods and how we think. Although such research is in its early stages and it is certainly unclear if this behavioral influence is actually occurring or to what extent, experiments on rats with gut microbes have certainly shown that it is possible. In one experiment, researchers replaced the gut microbes of a timid rat with those of a more gregarious specimen, and vice versa. It was found that the timid mice became more fearless and bold, while the previously outgoing and aggressive mice became timid and meek. What does this mean for human beings? The jury is still out.
Gut microbes have also been shown to influence our cravings for certain foods. Researchers from University of California, San Francisco (UCSF), Arizona State University, and University of New Mexico have found evidence to suggest that what we feel like eating may be the microbes signaling us and compelling us to ingest certain nutrients that they need rather than just making do with whatever comes their way. Our digestive system is basically an entire ecosystem of various types of microbes, all jostling around and trying to survive. The research suggests that different types of microbes require different kinds of nutrients, and when they are deprived of what they need, they create cravings for certain foods in us, such as sweet or fatty foods, through altering neural messages sent through the vagus nerve. They can also manipulate us in other ways to do their bidding, such as punishing us by producing toxins to make us feel unwell, or to conversely make us feel good through releasing chemical rewards. Since our digestive system is connected to our nervous system, there is a possibility that these microbial signals are influencing our behavior in other subtle ways as well, although it is not yet clear exactly in what way.
It seems clear that parasites and that viruses and microscopic organisms can exert an influence on our minds and behavior, but to what potential extent? Many are probably already wondering just how likely it is that some sort of mind altering virus could run amok or basically start a zombie apocalypse. In a way, it seems that it is certainly possible. For instance if the rabies virus were to mutate fast enough and in a way that allowed it to dramatically shorten its incubation period, decrease its fatality rate in order to allow more time to spread, and additionally become airborne, it could very well turn into something that resembles a zombie pandemic from a horror movie. Although rabies is now transmitted only through bites from infected animals, for it to become an airborne contagion is not a completely far out notion. All it would have to do is swap some of its genetic material with an airborne virus such as influenza, a process known as recombination and something that different strains of the same virus do all of the time, although rabies and influenza are far too dissimilar for this to feasibly occur in nature. With a very short incubation period, low fatality rate, and highly contagious means of spreading, and perhaps even more acute symptoms of aggression, carriers of the virus would essentially become mindless, furious vectors for the pathogen roiling within them, and it would spread beyond our ability to control it.
Of course if some shady military organization wanted to speed up the process, they could just go and make an aerosolized or engineered version of the rabies virus. Of the possibility of what a theoretical form of rabies engineered to be a zombie virus might look like, a professor in the Department of Cell Biology and Molecular Genetics at the University of Maryland, Jonathan D. Dinman, PhD, summed it up nicely in an interview with RedOrbit:
"So, you start with Rabies virus, but you engineer it so that it doesn’t actually kill you. It just takes over your brain and makes you want to bite other people to spread itself. Infected people just become automatons devoted to spreading the virus. The main viral property you’d want to change would be to convert it from causing an acute infection (like Ebola which tends to kill the victim quickly) to persistent infection (like Herpes, which stays with you for your entire life). Functions you’d want the infected person to retain would be metabolism (so they can produce more virus) and motility (so they can get from victim to victim). You would want the virus to cause infected people to lose the ability to think independently (and therefore come up with a cure)."
Some people think that such a virus has already been created. One persistent conspiracy theory is that a virus known as LQP-79 was created as a potential mind-control substance by the military, but it somehow made it into the outside world. This virus is said to cause profound mental deterioration and delirium, as well as savage cannibalistic urges, and is thought to be behind an infamous incident in Miami, when a man by the name of Rudy Eugene attacked homeless Ronald Poppo for apparently no reason and proceeded to try and bite his face off. It has also been linked to a spate of other such cases around the country, such as a man in a Staten Island restaurant who attacked and bit the ear off of another diner, either due to an altercation or the fact that he was not satisfied with the day’s special. There is even an “official” LQP-79 website dedicated to investigating the phenomenon. On the creation of LQP-79, the website claims:
"The LQP-79 virus is a result of the 79th attempt made at formulating a Lysergic Quinine Protein for use in diametric control of thought processes and the function of the mind."
The LQP-79 virus story is likely a hoax, as it has not been really covered in any reputable news source and has mostly been spread through internet discussions, but it has become immensely popular, so much so that the CDC even came forward to deny that such a virus existed, in order to squash all of the rampant speculation and quell panic. It is still a spooky story, though, and makes one wonder if such a scenario could ever play out for real, and if anyone is in fact working on some sort of zombie virus as a bioweapon, either working with rabies or something even worse. In light of the many examples of microorganisms influencing thought, it seems possible at least in theory.
Perhaps it would not even take some shadowy organization to concoct such a disease, but rather an entirely different sinister force; Mother Nature herself. Viruses are constantly mutating in nature, and some of these naturally occurring lethal pathogens, such as Ebola, Anthrax, and many others, are every bit as diabolical and deadly as something cooked up in a lab. Nature has a certain knack for coming up with truly wicked ways of invisibly killing us that are often difficult for us to combat or fully understand. A line from the movie World War Z says it up pretty well:
"Mother Nature is a serial killer. No one’s better, or more creative. Like all serial killers, she can’t help but have the urge to get caught or what good would all those brilliant crimes do if no one takes the credit? So she leaves crumbs. Now the hard part, is seeing the crumbs, the clues there. Sometimes it’s in your thoughts where the most brutal part of a virus is. Turns out to be the chink in its armor. And she loves disguising her weaknesses as strengths. She’s a bitch."
What is truly responsible for making us human? Is it our brains, our hearts, or is it at least in some part the doing of the tiny organisms that permeate our bodies and the environment around us? Are we truly in control of our own thoughts, moods, and behaviors? Or are we being guided, manipulated, and influenced by microscopic puppet masters with their own inscrutable agendas? Is there the potential for a new form of virus to assault us and wipe our humanity away? The next time you have a flash of anger, an uncontrollable urge do something, or simply an inexplicably craving for sweets, it might be good to wonder if that is really you, or the enigmatic will of the tiny forces sitting in the background, beyond your control and calling the shots.
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