It is not a question of if a killer asteroid will strike our planet, devastating at the very least a city, and at most the entire race. It is just a question of how soon. The current consensus: it won't be too long now.
A new study by a group called the B612 Foundation—a group dedicated to fighting the asteroid menace, which is a pretty weird mission, but its leadership includes real live astronauts and scientists, so let's take them as reasonable—finds that relatively large asteroids strike the earth with a pretty high frequency. Since 2000, earth-based sensors have detected 26 asteroid explosions at least as powerful as a nuclear bomb. None of them have landed upon our heads... yet. But the group's extrapolation of how often really, really big and bad asteroids hit our planet is pretty scary. From USA Today:
None of the 26 asteroids in Brown's data was big enough to destroy a city, because of their size and composition and because all exploded high in the atmosphere. But Lu says this database of harmless asteroids can be extrapolated to shed light on the frequency of their fearsome cousins. The results suggest that a city-killer strikes once a century, though Lu says he wouldn't be surprised if the true rate were actually less worrisome, perhaps once every 150 or 200 years or less frequent still.
Scientists quoted in the story say the data is somewhat scarce, and conclude that asteroids that can actually wipe a city off the face of the earth strike us with a frequency of once every...somewhere between 100 and 1000 years.
Still, this is a lot. Even if it's once every 500 years. Why build things? They'll be vaporized in spectacular fashion just a few centuries from now. Why have kids? Their great great great X 5 grandkids will just be burned up in a blinding explosion. Why try? We're just a tiny little marble in a washing machine of boulders, man.
Get that free love while you still can.