Eli5 What is sleep inertia, and why do we experience it?


What is happening when sleep inertia hits? Was there a need for it to happen? I would think that in the days of hunters and gatherers or constant states of war, sleep inertia would be a reason why many deaths have happened. I assume that the body is where it’s at today, due to the necessity at some period of time to have a biological function. There are a lot of terms surrounding it that are just hard to grasp for me.

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