A thousand years from now, when some vaguely human-like machine digs through the ashes of the Twenty-First century and tries to figure out what happened to those once-thriving animals called Homo sapiens, it may be confused about why an intelligent species that could build rockets and write songs like “Imagine” couldn’t heed warnings of its own destruction. A key question for future historians of the universe: How stupid were those humans anyway? What destroyed them?

Answer: Greed.