WHY do we age? When we are young, we seem invincible. We climb trees, frolick in the dirt, and happily share alarming amounts of mucus. In college, we can thrive on a diet of ramen and beer, party all night, and still take a test the next day. But at 30, we started to relax. It becomes more difficult to maintain muscle tone and avoid disease. Our joints start to ache and our memory starts to dim. And it’s mostly downhill from there.
People have long tried to stop or reverse this process. But the fountains of youth and the secrets of immortality remain firmly in the realms of fiction. Our bodies wear out, even if we no longer do the strenuous physical labor that our ancestors did. And the world seems determined to overwhelm us with a plethora of disease-causing microbes. To help defend against these pathogens, our bodies recruit other microbes, a large number of which reside in our intestines, where we feed them in exchange for their services. But as we age, this gut microbiota also becomes less effective at fighting disease.
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This raises an intriguing possibility. Perhaps the secret to longevity lies not in the body itself, but in our gut microbes. We still have a lot to learn about this complex set of bacteria, viruses, fungi, and archaea, but it turns out that people who reach a healthy old age often have distinctive gut flora. What’s more, we are finding ways to manipulate this inner world…