Cows. E. coli bacteria. Intestinal worms. Corn, rice and wheat. Man-eating tigers. Lice, crabs, fleas, ticks and (shiver) bedbugs.
These are some of the living things whose fates have been bound up most closely with our own in an ages-long dance of survival. They dwell in our cities and countrysides, in our houses, in and on our very bodies, and sometimes vestigially in our minds. Now consider the list above: If you were playing Noah (and to a great extent, as a species, we are, albeit clumsily), which species would you toss off the ark?
As N.C. State professor of biology Rob Dunn explains in his new book, The Wild Life of Our Bodies: Predators, Parasites, and Partners That Shape Who We Are Today, in a world of interconnected organisms, it's not always easy to distinguish friend from enemy (or, in some cases, "frenemy").
Take, for instance, intestinal worms. They've been largely eliminated in wealthy countries, which seems like a clear-cut victory for modern medicine and hygiene. But one increasingly tenable theory holds that the disproportionate prevalence of a spectrum of disorders in affluent nations—from allergies and asthma to diabetes and Crohn's disease—may be because we miss our worms.
As Dunn relates, our immune system evolved in concert with the life-forms that took up residence in us; without them, the system sometimes goes haywire and attacks itself. To be sure, not every mud-borne parasite is a benign symbiont. But the past decade has seen remarkable results from a new treatment for bad cases of bowel disease: a tall glass of Gatorade filled with worm eggs.
Of course, patients who enroll in these studies have to overcome the "ick" factor to down such vermicious libations. A revulsion for parasites doubtless conferred survival advantages on our ancestors (and, to be sure, Dunn doesn't suggest we roll out a welcome mat for lice, bedbugs and other bloodsuckers, but interestingly he connects them with the development of hairlessness, nomadism and xenophobia). But a morbid, out-of-control "ick" response can do more harm than good—witness the indiscriminate, and dangerous, larding of consumer products with antibiotics.
Perhaps the ultimate example of biophobia was the work of one James Reyniers, a researcher whose story Dunn tells in a fascinating early chapter. As a 19-year-old machinist and undergraduate biology student at Notre Dame, he undertook to create the first entirely germ-free lab animal. In 1935, after seven years of painstaking progress, he succeeded, and so, apparently, did his guinea pigs: "They seemed hungrier and more active than those on the outside with microbes ... The animals in the chambers seemed to live longer, too, and they never developed tooth decay."
These animals were invaluable to research, and they captured the imagination of a scientific establishment, and a public, entranced by the idea of a germ-free future. It turned out, however, that they needed special diets to survive. The microbes that normally flourish in their (and our) guts are essential to survival in the real world, providing valuable vitamins, enzymes and defense against harmful invaders.
"We imagine ourselves besieged by germs, but this is a mistake," Dunn writes. "Our bodies are integrated with the microbes ... While this new view of our lives is foreign to the medical community, to ecologists it is familiar."
The Wild Life of Our Bodies considers a wide range of questions from an ecological perspective, like the special relationship between man and cow, which helped us in ancient times but now threatens our health, as does our reliance on a massive cereal monoculture; and the chronic stress that results from the lingering memory of our predators, whom we have largely eliminated, in brains evolved to fight or flee.
The breadth of subject matter befits an ecologist, used to seeing the big picture, and a popularizer who's fluent in fields outside his specialty. Dunn is one of a new generation of scientists who have taken on the important mission of explaining science to the layperson, in books, magazines, newspapers and on the Web. Wild Life makes a case for a turn away from thoughtless biocide and sterile environments, back toward lives that more closely resemble those of our ancestors (where practical).
Acknowledging the complex webs of interdependence, developed over millennia, that have shaped who we are today can help us make more informed choices about whom to cohabitant with in the future. As he writes, "Whether it is worms, crops, or disease, the more we look, the more who we were and how we lived bumps up against who we are."