… is from pages 26-27 of historian Stephen Davies’s excellent 2019 book, The Wealth Explosion: The Nature and Origins of Modernity; Davies here describes one of the conclusions reached by Adam Smith and other Scottish Enlightenment scholars:
[A]s people became more connected to others, often distant, by the connections of trade and by social intercourse, and as their lives became more comfortable and less harsh so their psychology changed and they became gentler, less violent and aggressive and more controlled and ‘refined’ (to use a key term) in their way of behaving.