Persistence of consciousness.

The molecules making up microtubules, the protein filaments that form the internal “scaffolding” of your body’s cells, are replaced every 10 minutes. Actin filaments in the dendrites of your neurons are recycled even quicker: every 40 seconds. In fact, the entire brain’s composition turns over every couple of months. So how does your identity (not to mention memories, thoughts, and perceptions) manage to seem stable, consistent, and even solid over time? John McCrone discusses this problem, in a fascinating article.