Garrett Jones tells me that studies find a strong correlation between intelligence and conscientiousness (e.g., here), and he expects they have long been increasing together. The (good) book 10,000 Year Explosion (HT Kaj Sotala) guesses at mental changes induced by farming: less laziness, more self-denial and deferred gratification, better reasoning about trade, and more “self-domestication,” via less aggression and more acceptance of dominance by elites. Farming also brought war, marriage, and religion (beyond simple supernaturalism).
A key common thread here I think is “self-control.” While for the most part the intuitive inclinations of foragers tended to be well adapted to their circumstances, they also evolved social norms, such as against overt dominance, which used the threat of social sanctions to induce behavior contrary to ordinary inclinations. With farming, cultures evolved to hijack this norm mechanism to induce quite different farming-adaptive behavior, such as marriage, deference to elites, courage in war, and saving food for future needs. But this ability of culture to control behavior was limited by how much social sanctions could overcome other inclinations.
So it seems to me that if it was possible, the key change after farming would have been an increased sensitivity to culture, so that social sanctions became better able to push behavior contrary to other inclinations. This could have included genetic shifts, e.g., improved abilities to foresee sanctions and a stronger aversion to them, and cultural innovations, e.g., new forms of religion, patriotism, law, and policing.
This increased sensitivity to the carrots and sticks of culture generally appears to us as greater “self-control”, i.e., as our better resisting immediate inclinations for other purposes. And since we have more self-control in far mode, I suspect an important component of change since farming has been greater inclinations toward and abilities in far mode. Another reason to expect more far mode thinking is that intelligence seems to have increased and more intelligent people are better able to think abstractly.