There was a moment in human history when our entire existence may have desperately clung to a thousand or more people.

If every human on Earth vanished overnight, the planet would not hand its reins to chimpanzees, dolphins, or any other brainy mammal. A growing body of peer-reviewed research points instead to a far ...

Thousands of people disappear in the US every year, and the reasons are often more ordinary than you'd expect. Many cases ...