Here’s the story that people like to tell about the way we sleep: Back in the day, we got more of it. Our eyes would shut when it got dark. We’d wake up for a few hours during the night instead of snoozing for a single long block. And we’d nap during the day.
Then—minor key!—modernity ruined everything. Our busy working lives put an end to afternoon naps, while lightbulbs, TV screens, and smartphones shortened our natural slumber and made it more continuous.
All of this is wrong, according to Jerome Siegel at the University of California, Los Angeles. Much like the Paleo diet, it’s based on unsubstantiated assumptions about how humans used to live.