Once great monsters ruled the planet, and mammals cowered in the shadows and came out only at night. Now monsters once again rule the planet, and mammals are reverting to the nocturnal habits of their distant ancestors.

“All mammals were active entirely at night, because dinosaurs were the ubiquitous terrifying force on the planet,” says Kaitlyn Gaynor of the University of California, Berkeley. “Now humans are the ubiquitous terrifying force on the planet, and we’re forcing all of the other …