The Ecosystem You Carry

Your skin is not a wall. It is a coastline — and like every coastline, it is busy. Right now, in the creases of your elbows, in the warm dark between your toes, in the small continent of your gut, something like forty trillion individual living things are going about their lives. Eating. Dividing. Dying. Making chemicals your own cells cannot make without them. That number is not a typo. It roughly matches the number of human cells you contain. You are, by count, approximately half not-you. The word 'you' has always been doing more work than you thought. Here is the part that stops most people: remove them, and you do not become a purer version of yourself. You become a version that cannot digest properly, cannot regulate its own immune system, cannot, in certain documented cases, maintain a stable mood. Some of them live nowhere else on Earth — only on human skin, only on yours, shaped over thousands of years of mutual need into something that cannot survive without you, just as you cannot survive without them. Scientists have a name for the whole system: the microbiome. But that name flattens something stranger. You are not a body that carries passengers. You are a travelling world, and the passengers built the roads.