Evolution is all about processes that almost never happen. Every birth in every lineage is a potential speciation event, but speciation almost never happens, not once in a million births. Mutation in DNA almost never happens — not once in a trillion copings — but evolution depends on it. Take the set of infrequent accidents — things that almost never happen — and sort them into the happy accidents, the neutral accidents, and the fatal accidents; amplify the effects of the happy accidents — which happens automatically when you have replication and competition — and you get evolution.

Breaking the Spell (2006)