Book Review — Parasite Rex by Carl Zimmer
Yesterday, I finished Carl Zimmer’s “Parasite Rex: Inside the Bizarre World of Nature’s Most Dangerous Creatures”. Zimmer is an award-winning New York Times columnist and the author of 13 books about science. Three of his books have been named Notable Books of the Year by the New York Times Book Review. He prides himself on being the only writer after whom both a species of tapeworm and an asteroid have been named.
This book, first published in 2000, is about parasites and how they dominate our planet. Because we often don’t see the majority of parasites, even scientists neglected them for decades. Only relatively recently have they caught the attention of experts. And with that attention came a deep appreciation of the sophisticated adaptations parasites have made to their world, because it is so arduous to catch a glimpse of it.
The book is about the study of that life. And it is a grotesque study. I can imagine many people being disgusted as they read. For instance, there are 5,000 species of tapeworms, and the one we associate with human beings can grow inside us, in our intestines, to be 60 feet long. 60 feet is 18 meters! And you are just getting started. Let me tell you, there are some bizarre creatures out there. Cymothoa exigua, a crustacean, replaces a fish’s tongue. Sacculina, a barnacle-like parasite, uses a crab like a puppet. The Leishmania parasite chews away at the soft tissue of the head until its victim is faceless.
Little wonder that even in developed countries where irreligion is growing, a study focusing on eminent scientists, including biologists, revealed that they were significantly less likely to hold beliefs in the supernatural compared to the general population. Because as the knowledge of these strange, disturbing creatures became known, questions like why God created parasites arose. To keep us from being too proud, by reminding us that we were merely dust?
How did parasites get into us? Some argue that they must have been placed there by God since there was no apparent way for them to enter by themselves. Perhaps, they conclude, they were passed down through generations within our bodies to the bodies of our children. Did that mean that Adam, who was created in purest innocence, came into being already loaded with parasites? Maybe the parasites were created inside him after his fall.
But wouldn’t this be a second creation, an eighth day added to that first week — “and on the following Monday, God created parasites”? Well, then, maybe Adam was created with parasites after all, but in Eden, parasites were his helpmates. They ate the food he couldn’t fully digest and licked his wounds clean from within. But why should Adam, created not only in innocence but in perfection, need any help at all? Here, the catechism seems to have finally fallen apart.
“Parasites make up the majority of species on Earth. According to one estimate, parasites may outnumber free-living species four to one. In other words, the study of life is, for the most part, parasitology.”
But beyond reconciling theology with biology is the more important discussion of things like how our immune system, a complex web of functions, manages to help us against parasites. How the parasites manage to fool immune systems better than the best of our drugs. How parasites like plasmodium, which causes malaria, have caused changes to the evolution of our bodies over hundreds of thousands of years.
One of the things you will come away with from this book is how extraordinary evolution is. For instance, if a killer T cell, which protects you, recognizes signs of trouble, it commands a cell infected by a parasite to commit suicide. The parasite within dies along with it. Parasites are also not unintelligent. Evolution has taught them that pointless harm will ultimately harm themselves. So, for many, unless they have the right conditions to move to another host, they do not inflict so much damage as to kill off their hosts. In fact, blood flukes help the immune system kill some of their own because they don’t want overcrowding.
I very much enjoyed the case studies. Any time he mentioned Nigeria, my concentration level doubled. It was the case when he mentioned that in Nigeria, there lives a rare snail named Bulinus truncatus, one of the species that carry the blood flukes that cause schistosomiasis (a devastating disease). The sex life of the snail is exotic. Every one of them in Nigeria is a hermaphrodite, with male and female gonads it can use to fertilize its own eggs and produce clones. But some of them also come equipped with a penis, which they can use to mate with other snails. From studies, it appears these snails developed in such a way to use sex to prepare months in advance for an annual attack of parasites.
This book has so many interesting examples, anecdotes, stories, vivid descriptions, and speculations. It is the speculations that I have a slight issue with. The author sometimes speculates about the influence that parasites may have had on evolution and animal behavior. Though such speculations make for interesting thought experiments, they are by their very nature unverifiable.
I found the writing clear and well-organized, even if it goes on too long and is repetitive in places. But you have to admire how he was able to explain these complex creatures in a way that doesn’t make you feel ignorant for not knowing in the first place. You read it and become more aware of your surroundings and especially about what you put in your stomach. I wouldn’t be surprised if there have been people who turned vegan after reading this book.
That’s how educating and compelling the book is.
