A little more than a year ago, on a trip to Nairobi, Kenya, some colleagues and I met a 12-year-old Masai boy named Richard Turere, who told us a fascinating story. His family raises livestock on the ...

There’s a reason we tend to feel sleepy around the same time each night — and why, if we don’t set an alarm, we tend to wake up at the same time in the mornings. As long as we’re not pulling ...