Fortunately, the odds of an extinction-sized asteroid hitting the earth this century are low, on the order of one in a million. Unfortunately, asteroids aren’t the only threats to humanity’s survival. Other potential threats stem from bio-engineered diseases, nuclear war, extreme climate change, and dangerous future technologies.

Given that there is some risk of humanity going extinct over the next couple of centuries, the next question is whether we can do anything about it. We will first explain what we can do about it, and then ask the deeper ethical question: how bad would human extinction be?

Read more at "Preventing Human Extinction" at the Effective Altruist blog.