In 1803, 20 orphans boarded a ship in Spain. Though all of them looked healthy, one of them developed pustules eight days later. The pustules soon developed into scabs.
The child’s symptom, iconic of the dreaded disease smallpox, was not a catastrophe; in fact, it was exactly what King Carlos of Spain hoped. The child’s scab was scraped, and the scrapings were rubbed into scratches of the arm of another orphan. This orphan then developed scabs and the process was repeated until all of the orphans bore the distinctively scabbed arm. The ship went to ports around Asia and the Americas and delivered scabs to each port.
What seems like a disturbing scene from a David Lynch movie is actually the 19th century version of vaccination and is one of the many fascinating stories in Carl Zimmer’s new book Planet of Viruses. Zimmer is a long-time writer of popular science essays and books including Parasite Rex and Microcosm. In Planet of Viruses, Zimmer introduces a new virus in each chapter; the history of its discovery, how it’s treated and how researching that particular virus is important both to human health and understanding vast biological concepts.
For example, the chapter on human papillomaviruses (HPV) has the intriguing title “Rabbits with Horns.” Zimmer starts the chapter talking about jackalopes, the rabbits with antlers familiar to anyone who has visited rural Midwest or Western states.
“Most jackalopes are nothing but taxidermic trickery,” Zimmer explains in the chapter. “But like many myths, the tale of the jackalope has a grain of truth buried at its core.”
Zimmer then tells the story of a scientist who successfully caught a “horned” rabbit and wondered if these horns were actually tumors. The scientist ground up the horns and mixed them in a solution, which he then filtered to only let tiny viruses through. He then rubbed the solution on the heads of healthy rabbits. They grew horns as well, turning normal rabbits into jackalopes.
Zimmer masterfully hooks in readers who don’t necessarily find microbes interesting on their own. The book is 94 pages, a very fast read for the busy college student. In those 94 pages, he gives whirlwind introductions to viruses commonly known (such as the common cold, influenza and HIV) and to viruses unheard of to the general public (such as bacteriophages, marine phages and mimiviruses).
Though the latter categories seem like they should only be interesting to scientists in lab coats, there’s a reason Zimmer includes them in this book. The chapters are short, but he explores many broad scientific ideas that border on the philosophical.
Viruses are more than tiny microbes that make us sick; they can transfer genes between species, meaning about 8 percent of human genes are actually virus genes. Viruses can infect people and then become stripped of everything that makes people sick. Then the immunity to the virus and the virus genes are passed on to the next generation. The virus genes aren’t just useless hitchhikers; some of them have become useful for tasks like attaching placental cells to a developing fetus and thus have become essential to our own survival.
Zimmer beautifully describes this arrangement in his chapter “Our Inner Parasites” on endogenous (meaning “generated within”) retroviruses.
“In our most intimate moment, as new human life emerges from old, viruses are essential to our survival,” he writes in the chapter. “There is no us and them – just a gradually blending and shifting mix of DNA.”
Therein lies one of the most important, and awe-inspiring, concepts of biology. Separating life into distinct categories of species is useful for certain practical reasons but generates the misconception that we don’t interact very much.
In fact, nothing could survive if not for physical and genetic interaction. Even separating living from not-living can be a distraction from the continuum of diversity around us.
In his final chapter “Epilogue: The Alien in the Water Cooler,” Zimmer concludes that life “did not start suddenly with the flick of a great cosmic power switch. It’s likely that life emerged gradually, as raw ingredients like sugar and phosphate combined in increasingly complex reactions on the early Earth.”
Planet of Viruses is an interesting read for biology students and a fascinating introduction for non-scientists. It is an excellent primer in how life is all connected as told through the stories of its tiniest residents.
AMY STEWART can be reached at firstname.lastname@example.org.