And how does Darwinism explain the existence/development of “an evolved conscience”?
I'll refer you to the David Brooks column referenced in the original article:
in recent years there’s an increasing appreciation that evolution isn’t just about competition. It’s also about cooperation within groups. Like bees, humans have long lived or died based on their ability to divide labor, help each other and stand together in the face of common threats. Many of our moral emotions and intuitions reflect that history. We don’t just care about our individual rights, or even the rights of other individuals. We also care about loyalty, respect, traditions, religions. We are all the descendents of successful cooperators.In other words, cooperation and kindness and some degree of altruism were successful survival strategies, so they got fixed in human nature. On an individual level we experience the result as a conscience. That's simplified, but the basic idea.