Why My Brain Thinks I'm Falling Out of a TreeA vestigial reflex from our tree-sleeping ancestors

From the show

Oh, god... really?

The hypnic jerk is a biological misunderstanding between your brain and your muscles during the onset of sleep. Evolutionary biologists trace this phenomenon back to primate ancestors who needed to prevent fatal falls from tree branches. This sudden jolt acts as an outdated safety mechanism that confuses deep relaxation with a loss of balance.