I love how things like the 40 hour work week with two days off get enshrined as some kind of natural phenomenon that has always been with us. 40 hours is an arbitrary number that came from trade unionists demanding fair hours and Robert Owen's slogan: “Eight hours labour, eight hours recreation, eight hours rest.” I mean those two things: 8 hour work day and 8 hours of sleep have been considered to be the biological/…
Have you been sleep deprived ? There's a clear limit under which you're useless. For an extreme instance, I lost sleep for 5 days and went borderline insane.
Maybe 6h of sleep is adequate but saying 8 is arbitrary bulls$t is... exactly that.