Before that people relied on local solar time, where noon is whenever the sun is highest at the town hall. That's also socially constructed, just for a smaller social unit.

The only natural order of things for individuals is daylight where one is. In which case, one doesn't really need a clock at all, just the various natural markers like twilight, sunrise, and noon.

Of course, the whole notion of individualism is a relatively recent modern invention. Naturally humans are eusocial primates who live in close groups. So if you're after truly natural, "morning" is when your troop leaders get up and "evening" is when they start to bed down, and it's a thumping for you if you're noisy at the wrong time.

Alternatively, we could admit that modern society exists and isn't going away and work together come up with some useful global definition of social time that works reasonably well for all concerned.