Why do people have different inherent sleeping patterns that they gravitate to (e.g. some humans are morning people, whereas some are very nocturnal)?

Question

Why do people have different inherent sleeping patterns that they gravitate to (e.g. some humans are morning people, whereas some are very nocturnal)?

In: Biology

Answer 1

I don’t know why I know this and honestly I’m surprised I still do ;

When we were in tribes it made sense half the group stay awake and protect the tribe, and the other sleep. Then take it in turns.

If you think about hunters, they’d go early morning (e.g. sunrise) and evening (sunset) or use darkness, increasing chances of success (element of surprise)

Gatherers might go day time as there’s less predators, making it safer and visually easier to forage.

So we’ve probably evolved for different roles in society which we can still see today (day job vs shift work).