"It's so old,” she said, "that, had life developed, it would be billions of years older than we are. Imagine what such a civilization might be like.”
Dead, thought MacAllister. That's what it would be like. The fact that no technologically advanced species had been found in all these years made it pretty clear that the damned things have no staying power. You could see it at home, where, starting with the Cold War, there'd already been a few close calls.
It explained the Fermi Paradox. Nobody visits us because they blow themselves up before they get that far.