Societies and cultures are just the emergent results of the interaction of phenotypes. i.e. Culture and people are one and the same.
Let's consider biology. Physics and chemistry constrain biological processes and systems, for sure. But the number of distinct proteins based on the same set of amino acids, for example, is arguably unlimited (or at least, huge). Selection may favor one protein over another, and yet have virtually no impact on amino acid structure and diversity. Let alone on atoms, nucleons, quarks, etc.
The same applies to societies and cultures vs peoples.
Physics is just emergent properties of ... (math?). Chemistry is just emergent properties of physics. Biology is just emergent properties of chemistry.
It's turtles, all the way.