Interesting article by Mr. Pinker in the New Yorker. I tend to agree with some of his points, but the use of some sort of collective cultural memory when describing murder rates leaves much to be desired. A more simple explanation lies in the demand for violence, which is likely constant with humans, and the ability to experience physiologically significant proxies that satisfy the urge.
I argue the advent of hyper-realistic video games satisfies the killing urge and the resultant sales of various military simulation games certainly gives credence that both the supply and demand are there. Video games provide endless simulations that provide bloody restitution for various transgressions, and provide evolutionary "satisfactory" proxies for real conflict.
Admittedly, it’s hard to believe that today’s Southerners and Westerners carry a cultural memory of sheepherding ancestors. But it may not be the herding profession itself that nurtures a culture of honor so much as living in anarchy. All societies must deal with the dilemma famously pointed out by Hobbes: in the absence of government, people are tempted to attack one another out of greed, fear and vengeance. European societies, over the centuries, solved this problem as their kings imposed law and order on a medieval patchwork of fiefs ravaged by feuding knights. The happy result was a thirty-fivefold reduction in their homicide rate from the Middle Ages to the present. Once the monarchs pacified the people, the people then had to rein in the monarchs, who had been keeping the peace with arbitrary edicts and gruesome public torture-executions. Beginning in the Age of Reason and the Enlightenment, governments were forced to implement democratic procedures, humanitarian reforms and the protection of human rights.