Parasite Rex by Carl Zimmer

Dear blogging friends, hear me out: Don’t let the cover or the topic of this book (yes, it is about parasites) send you running. Let me first explain why you do, in fact, want to read Parasite Rex. You know when an author writes about a subject you never knew you cared about with such passion that you can’t help but have their interest rub off on you? That was my experience with Parasite Rex.

Okay, I have to confess I did suspect I might have some interest in parasites, a suspicion for which Scott Westerfeld’s Peeps is entirely to blame. But I never knew reading about them could be this interesting and enriching. Parasite Rex begins with a brief overview of the history of parasitology: until somewhat recently, Zimmer explains, the study of parasites and their impact on other life forms wasn’t taken very seriously at all, simply because they were considered too unimportant to have much of an impact. The Victorians, in fact, wrote about parasites with clear moral disapproval, which strikes us as an absurd approach to science writing today. As Zimmer says,

Parasites have been neglected for decades, but recently they caught the attention of many scientists. It has taken a long time for scientists to appreciate the sophisticated adaptations parasites have made to their inner world, because it is so hard to get a glimpse of it. Parasites can castrate their hosts and then take over their minds. An inch-long fluke can fool or complex immune system into thinking it as harmless as our own blood. A wasp can insert its own genes into the cells of a caterpillar to shut down the caterpillar’s immune system. Only now are scientists thinking seriously about how parasites may be as important to ecosystems as lions and leopards. And only now are they realizing that parasites have been a dominant force, perhaps the dominant force, in the evolution of life.

Zimmer thinks (and I agree) that the reason why parasitology as a field of study was neglected for so long is worth thinking about, because it says a lot about how we view the world and our place in it. The idea that they’re not complex enough to be relevant implies that there is a scale of beings, with certain living forms at the top (us) and others at the bottom. I have a quote I want to share that perfectly expresses what I’m trying to get at here, but it’s not from Parasite Rex. It’s from the essay “Bugs in the Brain” [warning: PDF link] by Robert Sapolsky:

Many of us hold the deeply entrenched idea that evolution is directional and progressive: invertebrates are more primitive than vertebrates, mammals are the most evolved of vertebrates, primates are the genetically fanciest mammals, and so forth. Some of my best students consistently fall for that one, no matter how much I drone on in lectures. If you buy into that idea big-time, you’re not just wrong, you’re not all that many steps away from a philosophy that has humans directionally evolved as well, with the most evolved being northern Europeans with a taste for schnitzel and goose-stepping.

As Zimmer points out when he tells us about parasitology in Victorian times, many of the scientists that despised them did subscribe to this philosophy, and often used parasites as metaphors for those they deemed socially undesirable. Fortunately, just like there’s been a shift in the way science views issues like class or ethnicity, there has been a change in how parasites are viewed.

Parasites are, in fact, very complex organisms, and their impact on their hosts over the millennia is significant enough for them to be one of the driving forces behind evolution, or even possibly the reason why sexual reproduction exists at all. And the things they can do! A parasite’s existence is a constant battle of wits with its hosts’ immune system. Mostly it’s not in their best interest to actually kill their hosts, for obvious reasons, but some of their tricks include castration, mutilation, disfiguration, and zombification—what Zimmer refers to “parasitic voodoo”. To put it simply, some parasite exert complete mind control over their hosts. They become their new brain; or, to steal another one of Zimmer’s metaphors, the hand inside the puppet.

It’s like something out of a horror movie—except, of course, it’s the other way around. It’s horror movies that are often straight out of nature. Carl Zimmer also writes about how this shift in our perception of parasites can be seen in modern horror and science-fiction. Alien is horrifying exactly because it’s pretty biologically accurate. And that scares us.

Parasite Rex is seriously fascinating. It’s not a book for the squeamish, but it’s so much more than a collection of “eww” moments. As one of the parasitologists Zimmer interview says, once you get to know them, parasites are not all that icky. They’re interesting creatures, and also adversaries worthy of our respect. Actually, “adversaries” is the wrong word altogether, as the stories about parasites being used as a form of biological pest control show. Just like the rest of nature, they can be useful, but they don't exist to serve us. Regardless of whether they work in our interest or against it, they’re important part of the ecosystems they belong to, and they're certainly worth taking notice of.

In case you’re wondering, the book is completely accessible to people without much of a science background—I should know, because I’m one of them. It’s also fantastically written: as you might have realised by now, Zimmer has a knack for metaphor, and he knows how to get his ideas across in a colourful and exciting way. Parasite Rex reads like a nature thriller. And like all my favourite science books, it’s a very humbling read.

Favourite bits:

Simply living within another organist—locating it, travelling through it, finding food and a mate inside, altering the cells that surround it, outwitting its defences—is a tremendous evolutionary accomplishment. But parasites such as Sacculina do more: they control their hosts, becoming in effect their new brains, and turning them into new creatures. It is as if the host itself is simply a puppet, and the parasite is the hand inside.

But all these works do have something in common: they play on a universal, deep-seated fear of parasites. This horror is new, and for that reason it’s interesting. There was a time when parasites were treated with contempt, when they stood for the undesirable, weak elements of society that got in the way of its progress. Now the parasites have gone from weak to strong, and now fear has replaced contempt. Psychiatrists actually recognize a condition they call delusional parasiotisis—a terror of being attacked by parasites. The old parasite metaphors, the ones used by people like Hitler and Drummond, were remarkably precise in their biology. And, judging from movies like Alien and The Faculty, so is the new one. It’s not just a fear of being killed; it’s a fear of being controlled from within by something other than our own minds, being used for someone else’s ends. It’s a fear of becoming a flour beetle controlled by a tapeworm.

We still go through life pretending that we are exalted above other animals, but we know that we too are collections of cells that work together, kept harmonized not by an angel but by chemical signs. If an organism can control those signs—an organism like a parasite—then it can control us. Parasites look at us coldly—as food, or perhaps as a vehicle. When an alien bursts our of a movie actor’s chest, it bursts through our pretences to be more than brilliant creatures. It is nature itself that is bursting through, and it terrifies us.

Other opinions:
Smart Bitches, Trashy Books

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