Spend enough time in a medical job and you’ll face unexpected and existential questions. The most curious may even come from your own family. Several Christmases ago I faced a doozey: “Daddy, why are we here?” I tossed back an excessively world weary reply: “because the microbes need us, darling” before resuming an indulgent post-prandial nap. Later, I apologized profusely, and substituted that old chestnut about “leaving the planet better than when you arrived.” Turns out my original answer was right: it’s a bug’s life, after all.
All hail author Ed Yong, and his remarkable book, I Contain Multitudes: The Microbes Within us and a Grander View of Life.  This was my holiday read and is one to pick up in 2019. Yong offers a one-stop shop for anyone needing to understand the micro-biome, micro-genome, and micro-virome. Turns out that this is everyone plying the biomedical trade, or inhabiting a body. The intriguing title is from a Walt Whitman poem arguing that it is our complexities and contradictions that make us who we are. 
It’s never a bad idea to be reminded of one’s own unimportance. For me “embracing” my microbiome has, hyperbole aside, changed the way I look at life. It is now easier to accept that I am both nothing special and something extraordinary. Because I am festooned with bugs I am never truly alone or truly independent. I love the idea that each of us is not just a person, but rather a zoo with an ecosystem. Because human cells make up less than half our body, I need to understand my “other self,” and even reconsider what “self” means.
Sure, the simplistic “us versus them” germ-theory helped to develop antibiotics, antivirals, and vaccines. However, the inability to understand interdependence has also spawned pan-resistant bugs. We need to dial down the microbiological blitzkrieg and aseptic genocide. As in many areas of life, it’s time to get along. Our microbiome is less a “villain” in need of destruction, and more a “roommate” in need of accommodation. We are stuck together and take turns providing for the other. It’s mutually-assured-survival as much as mutually-assured-destruction.
Despite all the “freewill” mantra, Yong points out how we humans are even prompted when and what to eat by our buggy cohabitants. We eat to keep them happy, and, in turn, they keep us safe. When we die we no longer feed them and so they eat us. They clean up the mess, and so continues the circle of life. Our immune system kills invaders, but is also a tenancy agreement between human and microbe. If balance is symbiosis then the loss of balance is dysbiosis…though you can call it disease.
Yong proffers evidence for why asthma, obesity, rheumatoid arthritis, colitis, even depression and autism, can be understood in terms more familiar to ecologists than doctors. Accordingly, the future of medicine invites terms more familiar to park rangers than bomber pilots. The glorious act of falling in love is no less wonderous even if the microbes create and sense the pheromones. Childbirth is still wonderful beyond words even though vaginal birth and breast feeding deliver essential bugs not just babies. Don’t get me started on kissing though: yuck.
Hominid history is fleeting next to the four billion years that microbes—bacteria, archea and single-celled eukaryotes—have ruled the roost. Multi-celled animals emerged so recently that we had to find accommodation on a planet where every niche was crammed. Humans are here because we cooperated, bodily and genetically. This includes the blessed-union that created our mitochondria.  Embracing our contractual obligations—rather than fighting tooth and nail—could be the next medical revolution.
We first met our microbiologic neighbours 200 years ago via microscope. This coincided with religion teaching that we were the “chosen ones” and Darwin arguing that life is a zero-sum “struggle.” We still over-label microbes (and anything we don’t understand) as pathogens, rather than mutualists or symbiotes. Even the term colonizer is unjustified: microbes were here long before us. As for why I and my feral children are here, I am not equipped to answer, but am lucky beyond-measure or merit. Accordingly, for 2019, my resolution is to be guided more by my microbe-filled gut.
Peter Brindley, professor in the department of critical care medicine, Department of Anesthesiology and Pain Medicine, and the Dosseter Ethics Centre, University of Alberta, Edmonton, Canada. He is on Twitter @docpgb
Competing interests: None declared.