As I was about to say before being so rudely interrupted by the site being down:
Brain researchers keep finding little bits and pieces of morality in brains themselves, which would indicate to me that a good portion of what we call morality is built into us. Babies recognize stealing long before they are old enough to talk, let alone define what stealing is. But I would assume that all genetically induced morals can be overridden by social demands, pressures and memes. The one child policy of mainland China isn't the same as eating your babies, but it's pretty damned close. And a consistently large portion of nearly every society isn't the least bit concerned about stealing being wrong, because those people do it all the time. So I tend to suspect that we have morality built in via evolution that works a lot of the time but not all the time.
AddHomonym certainly had it right in his post about cross-cultural moralities. For every instance you can find or cross-cultural similarities, there are, by definition, many instances where they are different. That's one of the reasons there are multiple cultures. If we all did things the same, we would all be one culture. And to think a group that never even heard of the christian god is being influenced by that one thing (morality) while that same god spent millennia making sure they hadn't heard of him otherwise is insane. An actual loving and caring god, after getting over the Babel thing, would have been nice enough to make sure his story was told in all of those languages. Those that think the post-Babel migration to all corners of the earth explains the different cultures seem to ignore the fact that none of those cultures far away from the area where christianity was born had heard a thing about it, nor did any of them have a story about being descended from a group whose language was suddenly changed. Cultures of old with story-telling traditions don't forget that much.
Most of us born with moral tendencies and successfully inculcated into society do adhere to a generally consistent list of moral standards. If we were all born sinners, as the christians claim, the world would be a much worse place. Every time someone was born again and started shouting "I'm saved" someone else would be running by with a club and bop them over the head. Something I have been tempted to do, but I'm too moral for that, even as an atheist.
Anthropologists have described some tribes found living deep in the Indonesian jungles who would fight each other in battles that consisted mostly of taunting, until one side or the other threw a spear and killed one of their opponents. Once one person died, the battle was over, and each side withdrew, one to celebrate, the other to plot revenge. The next year there would be another battle, and again, it would end when one person died, regardless of which side killed. This would go on for decades, with one annual death being enough to stop every battle.
In one battle, in one day, the British lost 16,000 men during World War I. I don't know how many Germans died that day, but I'm guessing it was more than one. Yet we call ourselves more civilized. And more moral.
I don't think so.
But whatever the source of our morality, we also have sources of immorality (money, sex, power) and apparently a percentage of every population falls into such traps. Societies seem always to have vacuums that can be filled by organized crime, and other vacuums to be filled by individual wrongdoers. Illegal drugs create a vacuum. The front door of a bank creates a vacuum. Bad guys fill them. But most of us are not tempted by such things, and that's good. Appreciate it.