August 16, 2026

You Are A Colony

My mitochondria comprise a very large proportion of me. I cannot do the calculation, but I suppose there is almost as much of them in sheer dry bulk as of the rest of me. Looked at in this way, I could be taken for a very large, motile colony of respiratory bacteria, operating a complex system of nuclei, microtubules, and neurons for the pleasure and sustenance of their families, and running, at the moment, a typewriter.

Lewis Thomas was a physician and pathologist who served as dean of Yale Medical School while writing short essays that turned hard biology into meditations on human life. This passage comes from his reflection on mitochondria, the tiny structures inside every cell that were once free-living bacteria before merging with our ancestors billions of years ago. Thomas wrote it in the early 1970s, at a moment when he was trying to explain to lay readers that the body is less a single unified thing than a vast cooperative arrangement. It matters now because it questions the idea of a solid, separate self — much of what feels like you is actually something else, still doing its own ancient work inside you.