On one view, the rise of natural philosophy over the last several millennia has slowly stripped man of his God-given dominion over creation and squeezed the human species into a tiny corner of the cosmos that, through accidents of physics, chemistry and evolution, happens to be our home. The diminishment of humankind is a trajectory that I find terrifying and exhilarating and it continues apace in Ed Yong’s masterful new book, I Contain Multitudes, which tells the stories of the microbes that swarm within and around us.
While we might preen at how far we have come in the past few thousand years, the whole of human history is but the work of a moment next to the three or four billion years that microbes – mostly bacteria, but also their cousins among the archea and single-celled eukaryotes – have ruled the roost. This is the point around which Multitudes pivots: precedence matters. The multi-celled animals and plants that emerged late in life’s story had to find accommodation on a planet where every niche was already occupied by invisible microbes. They had no choice but to interact, bodily and genetically, and through the blind thrashing of evolution, with the Earth’s microbiome. And we are only now discovering the extraordinary reach of the web of interactions spun from those turbulent processes.
The central idea is so obvious and so obviously important that we are stung like Huxley on learning of Darwin’s theory of evolution by natural selection: “How extremely stupid not to have thought of that!” The idea is not Yong’s, of course – it has emerged from over a century of research, much of it very recent. But he had the wit and the skill to wring from this mass of observations a tale that shifts our personal cosmology once more (informing us along the way that we have more bacteria in our guts than there are stars in the Milky Way) and compels us look anew at the world.
Multitudes starts out in the middle of the seventeenth century with Leeuwenhoek’s discovery, using his superior microscope, of tiny animalcules in a drop of pond water, and alights briefly on the well-known work of Pasteur and Koch who were central to the germ theory of disease that still dominates most people’s thinking about bacteria – their reputations remain mostly unfriendly. It fell to the microbial ecologists of the twentieth century to rehabilitate bacteria as a normal component of the planetary scheme of life. Though some microbes are parasitic and pathogenic, many have developed symbiotic relationships with their hosts. And as researchers have delved deeper, particularly since adding DNA sequencing to their toolkit in the 1970s (which makes it relatively easy to identify individual species and to catalogue their genetic and molecular capabilities), the richness and complexity of those relationships has produced surprise after surprise.
From this treasure-trove of research Yong pulls story after story: how luminescent bacteria colonise and control the development of light-emitting organs in the Hawaiian bobtail squid; how the beewolf wasp (since long before Fleming chanced upon penicillin) squirts its larvae with bacterial paste to give them the protection of antibiotics as they transform into adults; how human babies are slathered in microbe-infested mucus as they are delivered through their mothers’ vagina, the gift of life being accompanied by the gift of bugs to seed their childhood microbiome; how a mother’s milk is formulated not just to feed her baby but to keep those bacteria happy too; and how the microbes in its gut may well affect how that growing child thinks and behaves.
And those are just some of the naturally occurring effects. Now that researchers have started to get a grip on the world’s microbes, they are – naturally – trying to find them new forms of employment. Yong has tales of how microbial transplants are saving frogs in California, or allowing cows to feed on toxic plants in Australia, or stopping mosquitos from transmitting the dengue virus, or curing humans of chronic diarrhoea.
I do the book a disservice by just listing some of the contents – a pencil sketch of an oil painting. I Contain Multitudes presents, as the subtitle has it, “a grander view of life” and there are large hypotheses at play here, such as the idea of the immune system as an instrument for management of microbial co-existence rather than simply a brute defence against intruders; and of disease as dysbiosis, the result of imbalance or disharmony in the networks of our relations with different microorganisms. Things aren’t quite as hokey as the tree of souls in James Cameron’s Avatar but they’re more holistic than we have previously supposed.
The book is necessarily episodic in construction but Yong keeps a firm hold of the various threads, paying out his narrative like a master navigator. He has an easy manner that is nevertheless respectful of the material and the reader. The prose is smart, canny, and often quite beautiful. Yong has an enviable knack for metaphor. Here he is describing Carl Woese’s discovery of archea, one of the three great kingdoms of life: “It was as if everyone had been staring at a world map only for Woese to quietly unfold a full third that had been hidden underneath.” The rise of DNA analysis in biology is rendered simply as: “The gentle caress of the cotton bud replaces the swing of a butterfly net.”
The sure-footedness of the writing is a joy, but also instills confidence, as does Yong’s renunciation of the breathless wonder that sometimes infects popular science writing. He deals adroitly with the realities and incompleteness of research, dosing the text with warnings and caveats. We are carefully reminded of the limited relevance that laboratory studies may have for real world scenarios, and exhorted repeatedly not to confuse causation and correlation. And Multitudes is nicely illuminated by conversations with the “gleeful, imaginative, driven scientists” who have devoted their lives to investigating what is happening on the microbial front line. Yong has marvels aplenty to share, but makes room also for questions, uncertainties and disputes. This is a story that is far from finished and I would not be surprised if in five or ten year’s time a new edition is required.
Occasionally, Yong is hampered by his main players. I tripped over the long, unpronounceable Latin names – the likes of Bacteroides thetaiotaomicron or Algoriphagus machipongonensis – even though they are quickly neutered by abbreviation. More difficult to deal with is invisibility. Microorganisms are variously spheroid, rod-like or spiral in shape under the microscope, but remain out of sight in our daily lives, known principally by their effects on us and other creatures. These impacts are richly described in Multitudes, but even after we have become acquainted, our microbial companions feel strangely absent. Yong is not at fault here – this is simply the curse of the microbial (and the molecular) world.
I Contain Multitudes is hardly a light read – I closed the book with the feeling that Yong has peered into every microbial niche – but it is an endlessly rewarding one. In the realm of the life sciences there is a noble tradition of popular books that, by synthesizing emergent findings scattered through research journals, have reshaped our view of the world, peeling away the old, familiar veneer to reveal inner workings of unimaginable intricacy. In my own reading I think of Schrödinger’s What is Life, Dawkins’ The Selfish Gene and, more recently, Nick Lane’s The Vital Question. Among such company, I Contain Multitudes can hold its head high.
Ed Yong’s I Contain Multitudes can be ordered from the Guardian bookshop. @Stephen_Curry and his microbes are a professor of structural biology at Imperial College.
