The book is many things but most intriguingly it is a treatise on cellular existentialism.
The Tangled Tree by David Quammen,is a long, fascinating book that starts from a simple premise: what does the tree of life look like? In other words, how can we visually and accurately represent the evolution of various species to this present point in time? Lots of thinkers and scientists have tried to illustrate that notion and, as it turns out, they are all probably wrong. Because it seems the neat lanes for individual species don’t really exist. Instead, it’s a messy cellular swap meet between various life forms.
After laying the historic groundwork about how science has thought of this quest, Quammen switches gears and uses the life and career of contemporary scientists working in the field—in particular, Carl Woese—to move readers to a fascinating concept, namely, that humans are, at best, a collection of human cells that have borrowed bits and pieces from the cells of bacteria, and colonies of actual living bacteria on us and in us and that we need these parasitic cells to stay alive.
It’s equal parts history, biography, an ode to science, a survey of current microbiology and a treatise on a kind of cellular existentialism.
Quammen is a strong writer with a conversational style and appropriate moments of humor that never intrude, and also provides some alarming insights, such as this little nugget about antibiotic-resistant infections:
“What has driven this grim, costly trend is not just the use of antibiotics but also the reckless overuse of them for foolish or unnecessary purposes — doctors pandering to patients, for instance, by prescribing antibiotics for those who want to believe it will cure a viral infection. Antibiotics target bacteria exclusively and have zero effect on a virus. You might as well try to hose the dirt from your driveway using a flashlight. Another contributing factor is agricultural use: feeding low doses of antibiotics routinely to domestic livestock because that somehow increases their rate of growth. In the United States during a recent year, more than 32 million pounds of antibiotics were sold for use in livestock and most of that went for growth promotion regardless of whether individuals were sick.”
And when talking about two foot-eating strains of bacterial infection:
“The US Centers for Disease Control and Prevention promptly issued a warning that, because the gene was jumping around so deftly, from gut-dwelling bacteria into skin-rotting bacteria, “additional VRSA infections are likely to occur.” No one’s feet were safe, and especially not those of anyone foolish enough to walk barefoot in a hospital.”
Following the various people behind this research, a “tree of scientists” was illuminating, but slow going—it’s a long list of characters to keep straight. But I appreciated reading more about the men and women who helped move science forward. It felt a little cautionary as it’s clear science today is no longer funded in a way that allows the accumulation of knowledge at such a slow pace—instead, it currently requires monetizing breakthroughs, click-generating headlines and shareholder-pleasing patents. This detour through a kind of golden age of research, even though marked by plenty of obnoxious personalities and petty little ego wars, was heartening but also alarming in it’s absence.
But it’s the recognition, based on carefully presenting the accumulating science of microbiology, that humans are—at best—part bacteria, is the real payoff.
“The realization that bacteria and other microbes inhabit the healthy human body goes back a long way, at least to the day when Antoni van Leeuwenhoek scraped some plaque off his teeth and looked at the stuff through one of his lenses…But the shock that Leeuwenhoek experienced, finding alien creatures in his own mouth, would be matched later by the shock of finding alien genes in our genomes, let alone the whole menageries of intact microbes thriving amid the various compartments and surfaces of our bodies.”
“When I say “these particular bugs” are participants in peoplehood, I mean a whole roster of resident and combinations of residents within and upon the human body, differing somewhat from person to person and changing with the circumstances and time…The composition of resident microbes for each is contingent— contingent on who we are, what we do, how we’ve been born and raised, where we go, what we eat. And its contingencies have impact.”
“A recent estimate suggests that each human body contains about thirty-seven trillion human cells. It also contains about a hundred trillion bacterial cells, for almost a three-to-one ration of bacterial to human…and this doesn’t even count all the nonbacterial microbes—the virus particles, fungal cells, archaea, and other teeny passengers—that routinely reside in our guts our moths, our nostrils, our follicles, on our skin and elsewhere around our bodies. These stowaways may represent more than ten thousand species.”
By the end of the book, it becomes clear that rather than sitting atop some linear tree of life, we humans are barely us, and just moderately successful beneficiaries of this constant exchange of DNA and RNA and cellular flotsam and jetsam. We are part human, part bacteria and a walking habitat for a swarming biome of critters that live upon and in us and ultimately determine the length and quality of our lives. Humbling, to say the least.
I highly recommend this fun, engaging, thought-provoking book but be prepared to have the tree of life concept chopped down and a kind of cellular determinism left in its place.