Is it so surprising? The key takeaway could be rephrased “Healthy humans living under conditions similar to our evolutionary past naturally sleep an optimal amount of time at night.”

> When I get under 6 hours I see a clear drop off in performance.

Or is it “When I temporarily find myself in an environment with stress-levels similar to those of the people in the study I a) start to perform like them on modern day tasks and b) start to sleep like them.”?