Moral behavior is simply civil behavior, as opposed to instinctive (aboriginal, animal) behavior. All that is required for an individual to recognize his/her own best interest in civil behavior is to be able to see the consequences a year or more into the future.

All we need is a nation of individuals who can do that consistently, and we would have no further need for religion.

The fact that every human population of more than a few family units in recorded history (archeological records included) has been religious does, however suggest a competitive advantage.

Even the most hardened anti-social individuals recognize their own best interest in everyone else behaving civilly. Some carrot and stick enticements are clearly required, and regular reminders are probably useful as well.