This only makes sense if your underlying assumption is that the less violent are reproducing more offspring now. Your reference study merely shows that the phenotypical traits have a strong correlation with the behavior traits (in at least foxes). This selection requires offspring but its seems the parent is referencing a hormonal change due to social behavior.
I agree with the premise, that social and environmental norms can influence hormones, but the fox study is a different phenomenon altogether.
I agree with the premise, that social and environmental norms can influence hormones, but the fox study is a different phenomenon altogether.