11. I CONTAIN MULTITUDES
“I have observed many tiny animals with great admiration,”Galileo marveled as he peered through his microscope — a tool that, like the telescope, he didn’t invent himself but he used with in such a visionary way as to render it revolutionary. The revelatory discoveries he made in the universe within the cell are increasingly proving to be as significant as his telescopic discoveries in the universe without — a significance humanity has been even slower and more reluctant to accept than his radical revision of the cosmos.
That multilayered significance is what English science writer and microbiology elucidator Ed Yong explores in I Contain Multitudes: The Microbes Within Us and a Grander View of Life — a book so fascinating and elegantly written as to be worthy of its Whitman reference, in which Yong peels the veneer of the visible to reveal the astonishing complexity of life thriving beneath and within the crude confines of our perception.
Artist Agnes Margin memorably observed that “the best things in life happen to you when you’re alone,” but Yong offers a biopoetic counterpoint in the fact that we are never truly alone. He writes:
Even when we are alone, we are never alone. We exist in symbiosis — a wonderful term that refers to different organisms living together. Some animals are colonised by microbes while they are still unfertilised eggs; others pick up their first partners at the moment of birth. We then proceed through our lives in their presence. When we eat, so do they. When we travel, they come along. When we die, they consume us. Every one of us is a zoo in our own right — a colony enclosed within a single body. A multi-species collective. An entire world.
All zoology is really ecology. We cannot fully understand the lives of animals without understanding our microbes and our symbioses with them. And we cannot fully appreciate our own microbiome without appreciating how those of our fellow species enrich and influence their lives. We need to zoom out to the entire animal kingdom, while zooming in to see the hidden ecosystems that exist in every creature. When we look at beetles and elephants, sea urchins and earthworms, parents and friends, we see individuals, working their way through life as a bunch of cells in a single body, driven by a single brain, and operating with a single genome. This is a pleasant fiction. In fact, we are legion, each and every one of us. Always a “we” and never a “me.”
There are ample reasons to admire and appreciate microbes, well beyond the already impressive facts that they ruled “our” Earth for the vast majority of its 4.54-billion-year history and that we ourselves evolved from them. By pioneering photosynthesis, they became the first organisms capable of making their own food. They dictate the planet’s carbon, nitrogen, sulphur, and phosphorus cycles. They can survive anywhere and populate just about corner of the Earth, from the hydrothermal vents at the bottom of the ocean to the loftiest clouds. They are so diverse that the microbes on your left hand are different from those on your right.
But perhaps most impressively — for we are, after all, the solipsistic species — they influence innumerable aspects of our biological and even psychological lives. Young offers a cross-section of this microbial dominion:
The microbiome is infinitely more versatile than any of our familiar body parts. Your cells carry between 20,000 and 25,000 genes, but it is estimated that the microbes inside you wield around 500 times more. This genetic wealth, combined with their rapid evolution, makes them virtuosos of biochemistry, able to adapt to any possible challenge. They help to digest our food, releasing otherwise inaccessible nutrients. They produce vitamins and minerals that are missing from our diet. They break down toxins and hazardous chemicals. They protect us from disease by crowding out more dangerous microbes or killing them directly with antimicrobial chemicals. They produce substances that affect the way we smell. They are such an inevitable presence that we have outsourced surprising aspects of our lives to them. They guide the construction of our bodies, releasing molecules and signals that steer the growth of our organs. They educate our immune system, teaching it to tell friend from foe. They affect the development of the nervous system, and perhaps even influence our behaviour. They contribute to our lives in profound and wide-ranging ways; no corner of our biology is untouched. If we ignore them, we are looking at our lives through a keyhole.
In August, I wrote about one particularly fascinating aspect of Yong’s book — the relationship between mental health, free will, and your microbiome.