Sleep is a vital function that has been preserved in every species we've studied to date. In episode 126, Matthew Walker explains how sleep is genetically hardwired and how hunter-gatherer tribes sleep as a group to mitigate risk. In episode 250, Nir Eyal shares time management hacks, including scheduling time for sleep and avoiding screens in the bedroom. In the same episode, Matthew Walker discusses sleep pressure and how caffeine blocks the sleepiness signal.