Discovering the great indoors

There’s a hidden world of insects, fungi and bacteria we have yet to plumb in our very own homes

It is easy to think today that we know most of what there is to know about life on Earth. But most living things have yet to be discovered or named, much less studied. We are surrounded by our own ignorance. This is even true in the wilderness of our indoor spaces — our homes, schools, offices and other enclosed places. These, too, are terra incognita. But we can be the Darwins of our own basements, attics, bedrooms, kitchens and bathrooms. What we find is likely to surprise us.

The study of the life indoors began in earnest with the work of Antonie van Leeuwenhoek (16321723), a Dutch microscopist. Leeuwenhoek studied the life around him in his home and town with an obsessive sense of wonder. But over time, the observation of life indoors came to focus on dangers, like deadly microbial pathogens or their insect vectors, and how to kill them, while the search for new or unstudied species focused on old-growth forests, remote islands and deep seas. Only in the last decade or so have scientists begun to seriously document life indoors, revealing marvel after marvel.

In one study I was involved in a few years ago, we sought to find all of the arthropod species (insects, spiders and their kin) in 50 houses in Raleigh, North Carolina, United States. We expected to find a few dozen species. We found more than a thousand. In another study of 1,000 homes across the United States, we found tens of thousands of bacteria species, most of them unstudied, many new to science. Inside those homes we discovered more kinds of fungi than there were named fungal species in North America.

These species can have interesting stories, stories with consequence. Sometimes the consequences are bad. Nontuberculous mycobacteriae, which can cause lung infections, appear to be relatively common in shower heads, for instance. More often the consequences are good, or delicious even. Microbes in homes also contribute unique flavours to sourdough breads, homemade yogurts and kimchis. And these furtive indoor inhabitants can offer benefits to society as a whole. The genes used as insecticides in transgenic corn crops come originally from a bacteria species found in a flour moth of the sort that often invades kitchen cabinets. Understanding life indoors is becoming increasingly important because, increasingly, it is where we are spending nearly all of our time. Children in New York City today can sometimes spend up to 90 per cent of their average day inside, bathed in indoor life. The presence of pathogens indoors can obviously make children sick. But children can also develop allergies, asthma and other chronic diseases when they aren’t exposed to particular microbes missing from their homes and daily experience.

Several years ago, a project called Foldscope began producing very cheap microscopes nearly as high powered as those used by Leeuwenhoek. These “foldscopes” can be attached to phones and used to photograph microscopic species and their behaviours. More recently, my colleagues and I have developed a project called Never Home Alone on the inaturalist.org platform, which allows people to record and share their observations of indoor arthropods with scientists and naturalists.

To be part of this project, all you have to do is download the app, sign up and begin taking pictures of the wildlife you see in your home. You can then upload the images to the project page, where they will be identified by a community of naturalists. This effort is a little more than a month old, but already photos of roughly 800 species have been sent in and, already, there have been surprises. For instance, a giant crab spider — roughly the size of a human head — is far more common in tropical Asian homes than we expected. At the moment, you can help by taking photographs of microscopic species or macroscopic arthropods. But imagine a time when people around the world will take dust samples in their homes, or in hospitals or schools, and identify all of the species within. The bacteria. The fungi. The protists. The tardigrades! So far no large-scale study has systematically looked for these plump and nearly microscopic eight-legged animals in our homes. Or completely surveyed the viruses indoors. There is so much to do, and so much we can do together, as we embark on our own voyages of discovery without ever leaving home.

■ Rob Dunn is a professor of applied ecology at North Carolina State University and author of the forthcoming book, Never Home Alone.