[tayo42]

There's a lot, the appeal to how humans lived 10k years ago seems odd though. Just because they lived in a certain way doesn't mean it's optimal. This is plainly obvious when you look at diets. Just because something was done out of necessity doesn't mean it's right. Weak argument right off the bat.

[James_Henry]

I don't think he's using the appeal to say that the way pre-industrial people live is optimal. He's saying that maybe 7-9 hours isn't optimal.