Don’t mix up overeating with the human’s natural down phase during the mid day though. It’s normal for humans to feel tired after lunch, because humans took breaks during the day (kind of like Siesta in Spain).

Industrialization introduced the work from 9 to 5. In reality humans had a biphasic sleep schedule before that. We still experience some after-effects genetically from this in our circadian rythm. There’s actually several words in languages across Europe for this, i. e. in German “Mittagstief” (midday low).

Humans never worked as much for other people as they did this day and age, of course not counting the early days of industralization.