Who would be the best people to study to assess how science and society influence the expression of traits ?

Mostly, it would be social scientists however, some biologist could also explain these behavioral characteristics and temperaments like geneticists and cognitive scientists.
Variables and factors like the biological, environmental and evolutionary component of how a trait is unearth by these experts. 

The best field to assess this would be cognitive science for the main reason that people who fall under cognitive science can encapsulate a wide number of areas and characteristics and these help them explain how science and society can in end-effect influence the expression of traits. So I would say cognitive scientists and within that biologists and psychologists.

We can plant more trees and plants.