Debra Bruno is the author, with Bob Davis, of “Beijing from A to Z: An Expat Couple’s Adventures in China.”

Picture Rob Dunn approaching his publisher: “I have an idea for a book about all the tiny insects, bacteria, and other creepy-crawly things that live in our homes.” Then picture agents, editors, publishers and the general reading public, for that matter, shuddering and saying, “Nope.”

But we should be grateful that someone saw that “Never Home Alone: From Microbes to Millipedes, Camel Crickets, and Honeybees, the Natural History of Where We Live” would not only be utterly fascinating, but also turn out to be an important voice in the science-based argument in favor of more biodiversity.


That said, if you can read through the catalogue of things that invade our homes without wanting to get a hose full of bleach and power-wash every surface you see, you’re a stronger person than I. And if you can read about ancient humans picking lice off one another, or a cholera epidemic caused by an old diaper in a well, and then eat lunch, you have a stronger stomach than I.

But if you put aside the queasiness, you’ll find that “Never Home Alone” is a spirited romp through the vast diversity that inhabits our daily lives and how we’ve changed our ecosystems, often for the worse. Dunn and his colleagues estimate that they’ve found about 200,000 species inside our homes. A “ferocious diversity” of fungi, for instance, lives in our air conditioning systems, on the hands of bakers, on clothing, in drywall, on wallpaper and in our water systems.

Don’t be put off by the idea of wading through the microbes, viruses and microscopic living creatures that populate this book and our world. It’s not hard to love a scientist who partially justifies pursuing this line of research with the quip, “What the heck, I had tenure.” This is a guy who never talks about excretion. He talks about poop.

Dunn’s main theme, which he unrolls enthusiastically and colorfully, is this: “If ecologists have learned anything in the last hundred years, it is that when you kill species but leave the resources upon which they feed, the tough species not only survive but thrive in the vacuum created by the death of their competition.” What he means by “killing the species” is our aggressive overuse of anti-bacterials, antibiotics and other poisons, which has led to the growth of organisms that can survive these poisons and lead to worse infections.

This book will upend much of what we assume about the world around us. A few examples:

• Treated tap water has more bacteria than well water.

• The showerhead is a nasty place: Water that is both warm and pooled in the showerhead creates a swamp of potentially dangerous bacteria falling on our heads.

• Some bacteria in our systems might be able to reduce stress.

• Fungi will probably colonize Mars before humans do because they’ve been known to survive on “sterile” space stations.

• That funny smell when you turn on your AC in your house or car is the odor of fungi exhaling.

• Fungi hidden inside perfectly new and dry drywall might be connected to causes of Parkinson’s disease.

• Having high levels of fungi in homes doesn’t necessarily cause more allergies or asthma.

• Parasites in our systems, such as toxoplasma gondii transmitted by cat feces, can change our personalities, possibly even causing mental illness like schizophrenia.

• All adults have face mites. (An immediate effect of that factoid, in my case, was to cause me to Google “how to get rid of face mites” and rush to the medicine cabinet to see if our household had any tree tea oil.)

• One of the main causes of tapeworms in humans is letting dogs lick our faces.

“With bacteria, we haven’t even scratched the surface,” Dunn writes. But he is certainly scratching like crazy.

Dunn, a professor of applied ecology at North Carolina State University and at the Natural History Museum of Denmark, realized early in his career just how many unanswered questions there were in our understanding of the biological world. “I started to wonder,” he writes, “whether this phenomenon — of assuming someone else knows — is likely to be more common in homes than in other habitats, more common because homes are the place we are most likely to assume that someone else knows, most likely to assume that everything is more or less under control.”

The answer is yes, we do assume. And no, everything is not under control. “An entire world of animal life in plain view had been missed,” Dunn says, and is living on our windowsills, in the fur of our pets, inside our kitchen drains. “We know so little even about the animals around us,” he writes, “that we can’t preclude the possibility that some of the biggest discoveries yet to be made are those right where we wake up every morning.”

The story of cockroaches is only one of the compelling narratives. German cockroaches, Dunn writes, evolved to be repulsed by glucose because so many traps attracted cockroaches with glucose and then poisoned them. In fact, he writes, “resistance to our pesticides has evolved among bed bugs, head lice, house flies, mosquitoes, and other common insects in houses.”

Dunn’s advice: We need to let biodiversity back into our world and homes. In his case, he says, he plans to leave his windows open more often, get out in nature as much as he can and continue to study the kaleidoscope of natural life that enhances our world.

Never Home Alone
From Microbes to Millipedes, Camel Crickets, and Honeybees, the Natural History of Where We Live

By Rob Dunn

Basic. 323 pp. $28