Many science fiction movies have featured a “good guy” whose mind has been hijacked by an evil mad scientist and he is induced into bizarre behavior beyond his control. A closer look at this “idea” reveals that such brain hijacking is relatively commonplace in nature. I have tried to look for such instances for a month or so and I intend to compile my list here.
I must admit that I actually started wondering of such “real” parasites after a FANTASTIC talk by Daniel Dennett at TED and not after some creepy movie, I saw the talk about a year ago and was especially fascinated by Dennett’s start to the talk. Later i read a book by him, Breaking the Spell: Religion as a Natural Phenomenon that started on a similar note. This book is highly recommended, you must try to read it! Ofcourse the idea that Dennett talks about is old and was originated by Richard Dawkins, however i liked how he talks about the same.
Here basically Dennett talks on terrorism and gives a memetics based perspective on it, which can be said to be IMHO an extension of the famous Richard Dawkins essay “Viruses of the Mind”. The basic objective of the talk is applying evolutionary thinking to thinking, ideas and their flow and propagation. Wonderful talk, however i might write about the same in later posts.
Dennett opens the talk with a deceptively simple example of an ant.The start goes as:
So you are out in the woods or this pasture, and you see this Ant crawling up this blade of grass. It climbs up to the top, and it climbs and it falls and it climbs and it falls and it climbs, trying to stay at the very top of this blade of grass. What is this Ant doing? What is it in aid of? What goals is this ant trying to achieve by climbing this blade of grass? What’s in it for the ant?
And the answer is NOTHING! There is nothing in it for the Ant. Well then, why is it doing this? Is it just a fluke? Yeah it is just a fluke.
It is a Lancet Fluke, it’s a little parasitic brain worm that has to get into the stomach of a sheep or a cow in order to continue its life cycle. So salmons, you know swim upstream to get to their spawning grounds and Lancet Flukes commandeer this passing Ant, crawl into its brain and drive it up a blade of grass like an all terrain vehicle. So there is nothing in it for the Ant, the Ant’s brain has been hijacked by a parasite that infects the brain inducing suicidal behavior.
An analogy to the above is seen in humans, For example terrorists can be seen in parallel to the “Ant” i mentioned above with their brain been hijacked by “virulent ideas” (parallel to the lancet fluke) inducing suicidal behavior. It is more or less embedded in their brains and removing these toxic ideas is rather difficult. There are many other “ideas to die for”, like a lot of people have laid down their lives for Communism, Capitalism, Love can be said to be another brain parasite that can induce “abnormal” behavior. Others may be freedom, religion, etc.
Edit ( .4 July 2008. ) – Please Note a Clarification before continuing to read further: The usage of “to die for” is not in a negative light at all. It is only in terms of an outcome. Not if the result would be negative or positive. Just in the sense that they would influence behavior significantly. Please also note that i am NOT trying to suggest that something like freedom, or communism, love or religion is a parasite in the literal (and hence negative) sense. I am only saying that somebody bound by an idea will work for its propagation and hence what is interesting is how his/her behavior is influenced if bound by such an idea ( and yes ideas also mutate, but let us for the time being not consider that). Please note again that it is not in a negative sense. Also if there are some who still think that it is still in a negative light then i would suggest please have a look at the video, it is a brief talk by Dan Dennett and he talks about it beautifully, I think he would clarify the misconception in terms of what i actually mean and what might be perceived by a certain class of readers. I am NOT making a statement on what communism is about or what religion is about BUT about how such ideas influence our behavior ONLY. And it is a neutral perspective that way.
Basically “Ideas” are like lancet flukes, entering the brains of their hosts and encouraging them to work for the continuance of the idea rather than the host or his/her progeny. On the other hand, some ideas doubtless make their hosts more fit to survive and propagate, at least through this one mechanism, in a way they are similar to genes (that is why i mentioned that the basic scheme here is to apply evolutionary principles to how we think and behave). Such ideas as we are aware of are called as memes. The term meme was coined by Richard Dawkins in the now famous The Selfish Gene. Again a must read for those who have not read it.
Anyway, I had been thinking of more such examples. Not of “ideas”, but of real parasites that can infect the brain and induce “abnormal” behavior. And i tried to make a short list.
1. Toxoplasma gondii: This is by far the most interesting of the lot as it can “infect” humans too. This is a single celled parasite that lives in the guts of Cats, and sheds eggs which can be picked up by rats or other animals that can be eaten by a cat. T. gondii forms cysts in the hosts body, including the brain. The host otherwise remains completely healthy! It can look as fit as the non infected ones, can compete for mates and forage for food. However the most interesting thing came up after some research on T. gondii infected rats and normal rats. And it was found that T.gondii infected rats had no fear at all of cat odour, something by which they are normally terrified. Scientists continue that it is most likely that this happens so that the parasite in the rat can reach the intestines of the cat! If that is not weird enough then these can also infect humans too.
[Life Cycle of T. gondii – Photo Source]
Click to Enlarge
Humans can be hosts to T.gondii as well. People can get infected by handling soil or kitty litter. For most people it causes no harm. It can only be dangerous in cases wherein the immune system of the person under consideration is very weak. Thus people with immunity deficiency related conditions such as AIDS, and also pregnant ladies are advised not to handle kitty litter. Anyhow, in most cases the parasite lives peacefully in the body (and the brain). Since human brains have a lot of similarities with rat brains. It must induce some change in behavior. It is obvious that humans are too big to be eaten by cats, however there can still be some alteration. Studies showed that it had different effects on women and men. It can make woman more outgoing and kind hearted and men more jealous and suspicious. For more read this wonderful article: The Return of the Puppet Masters by Carl Zimmer.
2. Lancet Fluke (Dicrocoelium lanceolatum): I already spoke about this parasite earlier. However this time i hope to look at it in more detail. The Terminal Hosts of Lancet Flukes are cows and sheeps and intermediate ones are snails. These reach the inside of a snail through the excreta of cows and sheeps, the snail leaves them in mucus trails. The ants are attracted to these because of the scent and in doing so they ingest the fluke. They grow in the abdomen of the ant and then reach the “brain”, okay there is nothing like a brain in an Ant, but something like a ganglion. This induces suicidal behavior in the ant and clamps it to a blade of grass so that the fluke can complete its life cycle in the intestine of a cow or a sheep.
3. Rabies: Rabies is different from the above two yet similar in many ways. Rabies induces violent self destructive behavior in the host. Leading to biting and scratching. And obviously nothing can be more direct than that in spreading. Rabies is relatively well known than the above two, and rather different as it does not affect the brain directly so I would not write much in details about it.
4. Ampulex compressa: This one is macabre! Carl Zimmer again gives a graphic description of how it operates. But this one is like from the Science Fiction – Horror movies.
The wasp sits on the cockroach and slips its stinger through the exoskeleton into the brain. The wasp uses sensors to guide its way through the brain. It probes the brain till it reaches an area that controls the escape reflex, it then injects a venom there and the escape reflex disappears. The result from the outside is rather dramatic. The roach is not paralyzed, but it lifts its front legs and walks again albiet controlled by the wasp that uses its antennae to guides its movement. The roach crawls where the wasp leads it. Which is generally its burrow. The wasp then lays its eggs on the roach, the roach does not resist at all. The larvae then grows in the roach. Creepy!
5. Spinochordodes tellinii: This is another macabre example. Its larvae develop in insects such as grasshoppers and crickets. This parasite is able to influence its host’s behavior: once the parasite is grown, it causes its grasshopper host to seek out and jump into water, where the grasshopper will likely drown. The parasite then leaves its host; the adult worm lives and reproduces in water. Source
I will keep editing this post as and when i come across more such examples.