I Contain Multitudes: The Microbes Within Us and a Grander View of Life

by Ed Yong

heed Walt Whitman: ‘I am large, I contain multitudes.’5

the photosynthetic bacteria in the oceans produce the oxygen in half the breaths you take, and they lock away an equal amount of carbon dioxide.

there are more bacteria in your gut than there are stars in our galaxy.

The latest estimates suggest that we have around 30 trillion human cells and 39 trillion microbial ones – a roughly even split.

your right hand shares just a sixth of its microbial species with your left hand.

Milk is a mammalian innovation. Every mammal mother, whether platypus or pangolin, human or hippo, feeds her baby by literally dissolving her own body to make a white fluid that she secretes through her nipples. The ingredients of that fluid have been tweaked and perfected through 200 million years of evolution to provide all the nutrition that infants need.

In a large study of almost 10,000 people, Blaser showed that the presence or absence of H. pylori had absolutely no effect on a person’s risk of dying at any given age.

Our planet has entered the Anthropocene – a new geological epoch when humanity’s influence is causing global climate change, the loss of wild spaces, and a drastic decline in the richness of life.

Many familiar animals, including cows, elephants, pandas, gorillas, rats, rabbits, dogs, iguanas, burying beetles, cockroaches, and flies, regularly eat each other’s faeces – a practice known as coprophagy.

In other words, microbes shaped the evolution of the mammalian gut, and the shape of the mammalian gut influenced the evolution of microbes.

Yet despite the excessive hype, the concept behind probiotics is still sound.19 Given all the important roles that bacteria play in our bodies, it should be possible to improve our health by swallowing or applying the right microbes. It’s just that the strains in current use may not be the right ones.