Our Microbes, Ourselves: How the Trillions of Tiny Organisms Living Inside Us Are Redefining What It Means to Be Human
by Maria Popova
“You are mostly not you… We are not individuals; we are ecosystems.”
Being alone may be
the central anxiety of our time but, as it turns out, you are never really alone — at least in a biological sense: Every single cell of you — that is, every cell made of human DNA — is kept company by ten cells of microbes that call your body home. And because microbes are single-celled organisms that each carry their own DNA, the difference is even starker in genetic terms — you carry approximately twenty thousand human genes and two to twenty million microbial ones, which makes you 99% microbe. What’s more, although you and I are 99.99% identical in our human DNA, we are vastly different in our individual microbiomes — you have only one in ten of my microbes. Even more striking than the sheer number of these silent and invisible cohabitants is their power over what we consider our human experience — they influence everything from our energy level to how we handle illness to our moods to how tasty we are to mosquitoes.
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A quick primer here: Antibiotics work by killing harmful bacteria in our bodies with poison that is more toxic to them than it is to us. But because bacteria breed rapidly, they also adapt to evolutionary pressures fast. Antibiotics exert one such pressure, which means bacteria swiftly sidestep the poison’s effect by developing resistance to it. Like the spammers who are constantly outsmarting and bypassing our anti-spam systems, we end up bombarded with unwanted, harmful material despite our ephemeral defenses.
But apart from being largely ineffective in the long run, antibiotics have a darker and far more significant downside — they tamper with our microbiome, sometimes modifying it to a dangerous degree. They are especially perilous for newborns and young children — Knight notes that antibiotics in the first six months are associated with weight gain (which is hardly surprising, given we use antibiotics to fatten up livestock) and may put the child at greater risk for obesity in adulthood:
