Both segmented sleep and afternoon naps are recommended over a monophasic eight-hour block of sleep, but I don't see how they fit in with each other. Segmented sleep is the theory/hypothesis that people naturally sleep for four hours, stay awake for two, and then sleep for another four hours. There are references to "first sleep" and "second sleep" in many pieces of literature. But articles about segmented sleep don't really mention afternoon naps, even though they're supposed to be natural too. People feel more tired in the afternoon regardless of when they had lunch.
Are segmented sleep and afternoon naps mutually exclusive (e.g., if you sleep in segments you don't feel like taking an afternoon nap, and vice versa)? Is there evidence that people took siestas historically (before street lighting)?