But there was always that fear in the back of my mind that we might be living on borrowed time. So far, we’d found no explanation for the observed fact that all the intelligent species we’d discovered were in the range from the Stone Age–level Deltans to early spacefaring species like humanity, the Quinlans, and the Others. No elder races, no Heechee, no high-level Kardashev civilizations. None of us thought it was a coincidence, but no one had an explanation, either.
