Not necessarily. First of all, what 'advantageous' means has changed a lot. Our priorities and needs nowadays are completely different then back in early histo

Not necessarily. First of all, what 'advantageous' means has changed a lot. Our priorities and needs nowadays are completely different then back in early history. Food is abundant, physical work is much less common, etc. The benefits from having more awake time might not be enough to propagate such a change. Or the lost flexibility might have mattered much more back then. I'm not claiming everyman is clearly and strictly better than mono or biphasic sleep. We have to find out, and the only way we can find out is by people actually trying it. But saying that monophasic sleep is the only way to sleep is silly.