Humans evolved in caves and fields — not in sanitized homes, cars and schools. And our immune systems developed to find and suppress foreign invaders, growing stronger with each battle won.
~ Christine Peterson
It’s not there now, but I look forward to a time when we can essentially garden our homes — fill them with species that benefit us and push out the species that don’t.
~ ecologist Rob Dunn (on Fresh Air)
“Squirt, squirt, rub, rub, rub, rub.” The first lesson hospital volunteers (and staff, for that matter) learn is to sanitize your hands upon every entry and every exit from a patient room or medical area. This practice has shown significant reductions in in-hospital infections over the last few years — but also results in lots of either dried or gooey, but soft, hands among hospital staff and volunteers.
Out in the world, we are constantly exposed to a variety of germs that our bodies can usually deal with. As children, we develop resistance to the most common bacteria, and can (and should) be vaccinated against invasive viruses and uncommon germs. A result is that the occurrence of childhood diseases has plummeted over time in the U.S. and most other countries. (In fact, some ‘third world’ countries have higher childhood vaccination rates than the U.S. Think about that.)
However, today many have become concerned that children spend all their time indoors or in places that are too clean — and do not get the incidental exposures needed to develop resistance to common diseases. Wyoming science blogger, Christine Peterson, quotes author and doctor Jack Gilbert, “Keeping your kids too clean and away from healthy dirt and healthy animals seems to be a problem that triggers a wide range of immune-involved diseases not generally encountered among babies growing up in third-world villages.”
However, our homes aren’t quite as clean as we think, according to a report by Terry Gross, “Every surface; every bit of air; every bit of water in your home is alive,” says Rob Dunn, a professor of applied ecology at North Carolina State University in Raleigh. “The average house has thousands of species.”
I don’t think that any doctor (including Dr. Gilbert) would recommend growing up in a third-world village for your health, but exposure to a variety of microbes does nurture kids’ immune systems. Your house can be too clean. Dirt is a perfect medium for all kinds of microbial life. In fact, clean dirt — with reduced or absent microbes isn’t even a good growth medium for plants.
Rob Dunn considers the human body a microbial playground, “I find armpit bacteria fascinating.” Just like the human body, dirt is its own ecosystem, replete with a hierarchy of little critters that feed on the minerals and decaying organic materials that make up the bulk of the dirt. If you want to enrich your garden soil, you can add chemical fertilizer, but the best solution is to add manure or compost that comes with a thriving microbial community.
Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth’s body of soil is the pedosphere, which has four important functions: it is a medium for plant growth; it is a means of water storage, supply and purification; it is a modifier of Earth’s atmosphere; it is a habitat for organisms; all of which, in turn, modify the soil… it is considered an ecosystem by soil ecologists.
And just like in human society, diversity in nature is what makes a healthy community. The wide variety of microbes and other tiny creatures allow the soil community to adapt and respond to the naturally-occurring different conditions and changing populations, as well as external forces. The human body works the same way, in that we create our own internal community, in part, from the external forces in our lives. Exposure to a given hostile microbe allows the body to manufacture the proper antibodies to isolate or fight it. The body remembers these fights and can then reproduce the proper defenses for any future exposures.
In contrast, monocultures of single species are very fragile, and can be easy prey for external forces, either natural or man-made. Diversity allows the community to survive because it is not reliant on a single member of the community. For example, the community of poor Irish became principally reliant on the potato for food. When a fungus ravaged the crops in the mid-1800’s, extensive starvation occurred (and resulted in mass migration of Irish into America).
When Europeans first arrived in North America, they exposed natives to all kinds of germs from Europe that had not been present here before. Europeans had developed mechanisms to fight off those diseases, but Native Americans were defenseless. As a result, hundreds of thousands of Native Americans — whole tribes, in some cases — died of European diseases like smallpox and measles that had been inadvertently brought to these shores.
The extreme connectedness of our planet can similarly move previously localized microbial populations virtually anywhere on the globe in a matter of hours, disrupting the potential for natural acclimatization of the receiving population. We work to counter this with vaccinations, simply an introduction of the offending virus or germ in an inactive state that results in the body naturally amassing the defenses necessary to fight that disease. If you travel to certain countries, for example, you are required to obtain vaccination against the diseases prevalent in those areas before you go.
If an ecosystem’s strength is in its diversity, and human society’s strength is in its diversity, it seems to follow that an individual human’s strength requires diversity. Intellectual, spiritual and physical diversity makes us stronger. Maybe staying ‘too clean’ is a metaphysical analogy for living a more integrated life.
Getting down in the dirt (literally and figuratively) on occasion keeps us from becoming monocultural, unable to resist the natural chaos of our lives. It’s only human.
Terry Gross, Counting The Bugs And Bacteria, You’re ‘Never Home Alone’ (And That’s OK), November 12, 2018, Fresh Air, National Public Radio
Christine Peterson, Should We Let Kids Eat Dirt?, October 30, 2018, Cool Green Science
Steve Tarlton, Dirty Nature, June 5, 2015, Writes of Nature