The Crowd You Call Yourself

You think of your body as yours — one organism, singular, you. Take a census of the cells you are carrying and a stranger answer comes back. Enormous numbers of them are not human at all. You are something closer to a walking city than a single citizen.

Your gut alone holds trillions of bacteria — a whole ecosystem carrying many times more genes than your own body does, doing work you could not live without. They break down your food, school your immune system, and brew chemicals that climb to your brain and tug, quietly, at your mood and your cravings. When a hunger rises, it is not always you asking.

These passengers came aboard near birth and never left. Some lineages have ridden human bodies so long they have evolved to live nowhere else on Earth. They are as woven into being you as your own liver — and they are not you.

So the word "I" covers a negotiation: a truce between the human cells and the vast invisible nation living in and on them, voting, constantly, on what you'll want next.

And if so much of you isn't you — where exactly do you end?