What if some of the most important species facing extinction are living inside us? Our bodies are home to vast communities of bacteria, viruses, fungi and other microorganisms collectively known as the human microbiome. Many of these microbes have co-evolved with humans over thousands of generations, helping digest food, produce vitamins, interact with our immune systems and protect us from harmful organisms. But researchers are concerned that modern lifestyles—including widespread antibiotic use, highly sanitized environments and changes in how we live—may be contributing to the loss of microbial diversity from one generation to the next. Now scientists are working on an extraordinary idea: a Human Microbiota Vault. Inspired by the Svalbard Global Seed Vault, the project aims to preserve samples of humanity’s microbial diversity before potentially important microbes disappear—creating a kind of microscopic Noah’s Ark for the future of humanity. Could preserving the microbes of to...