A friend wrote to me regarding the "evolution of morality" and whether or not Islam would ever undergo the kind of transformation experienced in Christianity during the Reformation. After a brief introduction I wrote in reply:
But to the larger point, you're approaching morality as an atheist, not as either a Christian or a Muslim would, so you're bound to misunderstand their views. To both, there is no such thing as "the evolution of morality". Right and wrong are not a matter of debate and consensus; right and wrong are revealed by God.
What you see as the evolution of morality among Christians is actually a different phenomenon. Most of Christian history was dominated and warped by the Catholic Church, which propounded purposefully incorrect teachings about God's revelation to man (the Bible) to sustain its political power. With the Reformation, Christians as a whole reclaimed the gift God gave them and resumed interpreting the Bible in the correct manner rather than as a tool for social control. (People will argue over the term "correct", but the plain textual meaning of the words in the Bible are pretty clear.) This was not an evolution of morality per se, but rather an evolution of the Christian institutions towards the form they were intended to take in the first place.
As for Islam, Muslims they believe that their god, Allah, revealed divine truth though, primarily, the Koran. However, they are not faced with the potential for the same kind of institutional change that rocked Christianity because the existing Muslim institutions are interpreting the teachings in the Koran correctly and as intended. That interpretation is horrific, thus causing Muslims around the world to suffer.
Just my impression, though I'm no Islamic scholar. If I'm wrong, show me some sources.