What do you think poses the greatest threat to humanity?
Sandberg: Natural risks are far smaller than human-caused risks. The typical mammalian species lasts for a few million years, which means that extinction risk is on the order of one in a million per year. Just looking at nuclear war, where we have had at least one close call in 69 years (the Cuban Missile Crisis) gives a risk of many times higher. Of course, nuclear war might not be 100% extinction causing, but even if we agree it has just 10% or 1% chance, it is still way above the natural extinction rate.
Nuclear war is still the biggest direct threat, but I expect biotechnology-related threats to increase in the near future (cheap DNA synthesis, big databases of pathogens, at least some crazies and misanthropes). Further along the line nanotechnology (not grey goo, but “smart poisons” and superfast arms races) and artificial intelligence might be really risky.
The core problem is a lot of overconfidence. When people are overconfident they make more stupid decisions, ignore countervailing evidence and set up policies that increase risk. So in a sense the greatest threat is human stupidity.