Steven Pinker sees little reason to believe it has:
The reason that today, France and Germany aren’t likely to go to war, slavery is illegal, human sacrifice has disappeared, we don’t break heretics on the wheel, homosexuality has been decriminalized, and people are less and less likely to smack their children, is not that our hormone systems or brain wiring has changed by Darwinian forces. In most of these cases, the changes are too recent for generation-to-generation evolutionary changes (they unfolded over centuries, decades, or even years), and in most cases it is not clear how the less violent choices would have led to increased sexual attractiveness, fecundity, or survival. Of course I cannot rule this out in all cases (such as the decline in homicide since medieval times—it’s theoretically possible), but I don’t see any evidence that it has taken place.
Bryan Appleyard thinks this makes the current era of peace extremely fragile:
[I]s there something especially robust about these solutions we have found that makes them more likely to survive the cataclysms of history? If not, then the Pinker Peace is indeed a special case and nothing more.