Never Home Alone: A fascinating look at the creatures who share our homes

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

Never Home Alone: From Microbes to Millipedes, Camel Crickets, and Honeybees, the Natural History of Where We Live (2018) is a mouthful of a title. Which is only appropriate as abundance is one of the major themes Rob Dunn highlights in this utterly fascinating book. The rich, fecund abundance of life not of the world “out there” (though that, too) but the world “in here,” where we live — our homes. How rich and fecund? How about 80, 000 species of bacteria and archaea, tens of thousands of fungi species, and thousands of species of arthropods, along with a number of rodents. All found in a biological survey of a thousand Raleigh homes. And those are our uninvited guests. Dunn doesn’t ignore the ones we bring in willingly — our dogs and cats (who themselves bring in a host of hitchhikers). If our homes are our castles, they’ve been overrun.

But before you get too cringy about the whole idea, or decide to run out to the nearest hardware store for some traps and cans of Raid, Dunn’s message isn’t simply that we share our homes with a whole lotta creatures, but that this is a good thing. It’s their absence that we should fear, not their presence. And for as enthusiastic as he waxes about all that life in our basements, our drains, our showerheads, our bed linens, he’s equally depressed and disturbed over the disappearing biodiversity of our world — the little ones we inhabit all by ourselves or with our families as well as the single big one all of us share as one human race. Never Home Alone is both a joyful lilt and a dirge (or at least a warning cry).

Dunn opens with the statistic that the typical American child now spends “93% of his or her time in a building or vehicle,” a percentage not much removed from children in other parts of the developed world. We have become, in his words, “Homo Indoorus, the “indoor ape.” About time, he argues then, that we pay attention to what else is indoors with us.

After a brief jump back in time to show us the early discovery of bacteria/protists, focusing especially on Leeuwenhoek and Hooke of the 17^th Century, Dunn starts us off in one of the more mundane routines of modern daily life, the shower. More precisely, the showerhead, which he and other scientists have found is home to an abundant ecosystem of mycobacteria, biofilms that include “predatory bacteria swimming … like pikes through water … protists that eat the ‘pikes’ and nematodes that eat the protists, as well as fungi doing their own fungal thing. This is the food web that falls upon you as you bathe each day … trillions of individual organisms” (and you thought you were getting squeaky clean … ).

Well, at least, you might think, your water is “treated,” and it’s true that in most of the US water is treated with chlorine (or a similar agent), but in the sort of unintended consequence that Dunn returns to again and again, our destroying all the bacteria in treated water means we create the perfect environment for problematic ones to evolve and survive, which is why Dunn was able, for instance, to predict mycobacterial infections based on knowing if the water was municipal (treated) or well water (untreated). As he puts it, “our fanciest water treatment technology is creating water systems filled with microbes that are less healthful for humans than those found in untreated aquifers.”

Before you dismantle and sterilize your showerhead though, Never Home Alone throws in a twist. It turns out that not all such bacteria are bad (in fact, Dunn highlights, only about a hundred species of bacteria, protists, and viruses are truly inimical to humans). One type, Mycobacterium vaccae, appears to diminish stress in mice, so perhaps that relaxing shower is due to not so much from the warm water falling on your face, but the teeming biofilm falling with it. (If you’re still worried, Dunn does note only people with immune issues are at any minimal risk, and also that plastic showerheads seem to be more resistant to colonization by biofilms than metal ones.)

Somewhat similarly, that lowly cave cricket hiding in our basement turns out to be of potential benefit as well. Its digestive bacteria, which allows it to survive in the nutrient-poor environments of our cellars, also, Dunn has shown via experiment, can break down one of our most toxic industrial waste products: black liquor, a highly alkaline byproduct of paper making that has to be burned because it is too toxic to store safely anywhere. Oh, and that thief ant wandering off with a grain of sugar from your cupboard? Turns out it might also be carrying just the antibiotic we’re looking for. Maybe therefore, given the potential benefits these tiny creatures offer up, we should stop killing them.

This is the twin track of Dunn’s Never Home Alone: a contagiously effusive and enthusiastic sense of wonder of just how much life there is right before our eyes or under our feet that we just don’t notice in our day-to-day lives, and a constant sense of dismay over how we keep making the same mistakes, our indiscriminate chemical assault on that life wiping out not simply both bad and good together (the pests and non-pests, the dangerous and beneficent), but wiping out mostly the good by creating an “enemy-free space” because “resistance is quick to evolve among species we don’t like and less likely to evolve among the rest of life … including the natural enemies of the pests we are trying to control.” Put another way:

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 … in what ecologists call “competitive release.”

Our obsession with sanitizing everything, wiping out the creeping, crawling and flying creatures we share the world with, and waging antibiotic warfare on every little sniffle has only created a world where we suffer more from allergies and asthma and where pathogens are becoming ever more quickly resistant to even our antibiotics of “last resort.” A less biodiverse world is not only a duller world, but also a less safe one. Vaccinate your kids, wash your hands, drink only clean water, yes. But also open your windows more often, get dirty now and then, and put down the Raid.

Never Home Alone is endlessly fascinating and I could discuss so many such examples that this review would be nearly as long as the book (I highlighted a huge amount of lines). This is a book, after all, that encompasses German cockroaches and home baked bread, social spiders and Korean kimchee. Beyond the captivating details, it is as well always engaging, filled with sparkling wonder and scientific curiosity as it glides smoothly back and forth across time to provide historical context, and is utterly convincing and compelling in its heartfelt call to return biodiversity to our lives and the world. Highly recommended.