We started out with moral sentiments and intuitions, which is also where we find the greatest continuity with other primates. Rather than having developed morality from scratch, we received a huge helping hand from our background as social animals. ...
At this point, religion comes in ... While I do consider religious institutions and their representatives — popes, bishops, mega-preachers, ayatollahs, and rabbis — fair game for criticism, what good could come from insulting individuals who find value in religion? And more pertinently, what alternative does science have to offer? Science is not in the business of spelling out the meaning of life and even less in telling us how to live our lives. We, scientists, are good at finding out why things are the way they are, or how things work, and I do believe that biology can help us understand what kind of animals we are and why our morality looks the way it does. But to go from there to offering moral guidance seems a stretch.
Even the staunchest atheist growing up in Western society cannot avoid having absorbed the basic tenets of Christian morality. Our societies are steeped in it: everything we have accomplished over the centuries, even science, developed either hand in hand with or in opposition to religion, but never separately. It is impossible to know what morality would look like without religion. It would require a visit to a human culture that is not now and never was religious. That such cultures do not exist should give us pause.
... what would happen if we were able to excise religion from society? I doubt that science and the naturalistic worldview could fill the void and become an inspiration for the good. Any framework we develop to advocate a certain moral outlook is bound to produce its own list of principles, its own prophets, and attract its own devoted followers, so that it will soon look like any old religion.