Not exactly a shocking revelation, but humans aren't purely logic-driven beings.
My dog does OK with a philosophy of pure materialism, I figure I can, too.
The primary opposing viewpoint is moral realism, which holds that statements like "Intentionally killing an innocent person is immoral" are both meaningful and capable of being evaluated as a truth claim.
In general, I believe the ability of a social animal to restrain "baser" instincts would be referred to as social cooperation. For humans, a moral realist would say that while morality is closely related, it also can't be reduced to merely social cooperation.
Sure, I'd buy that. But I will also stand by my assertion that what you're calling "social cooperation" is sufficient for a workable morality to emerge. At no point is there a necessity for religion.
(Note that I'm not saying this is unique to Christians, or that it applies to all or even most Christians. Here endeth the disclaimer.)