> unbroken and uninterrupted eight hour sleep schedule didn't exist and is in fact, a totally modern invention and a consequence of the rigid 9-5 work schedule

> An unbroken eight hours of sleep did not always fit with the cycles of the sky above and sleep was therefore rhythmically polyphasic.

I tend to disagree. There is serious literature suggesting this, but to my knowledge no concrete evidence confirms it. In fact the industrial age did not arrive uniformly to all societies on Earth. We should have seen polyphasic sleep practice long ago in non-industrialized nations. Anyone aware of anything like this?