I read the link and scanned the articles cited. All they are talking about is from post agricultural sources that never heard of the pinal gland!
People were up at night because they had civilization to tend to, or they just woke up. Big deal. Show us some science.
My understanding of sleep is this- You need good full night's sleep because of circadian rhythms. Nature provides. The process starts when it gets dark, and this kicks in the pinal gland, which releases melatonin. Melatonin does some things to help to sleep quickly, and it sets off a night-long process of hormones activity that is doing things to help you rest all night then wake up right.
Modern living wreaks havoc on the natural melatonin-driven sleep process. I'm pretty sure that people living in the early days of cities had noise and disruptions just like we do.
I'm pretty sure Paleo folks went to bed at dark and woke up when the sun came up. Ever go backpacking for a week in the wilderness? (No lights, no beer, just elements) You start doing that too in just a couple days.