“Many people would agree that it’s more likely than not that we’ll eventually do ourselves in. And in fact, some astrobiologists theorize that all advanced civilizations hit the same insurmountable developmental wall we have. They call it the Great Filter. It’s a notion that’s often invoked to explain why we’ve never been visited by extraterrestrials.
“But there is another possible reason for the celestial silence. Yes, the Great Filter exists, but we’ve already passed it.” [1. Or those pesky Bracewll probes have gone astray.]