Why is belief in a higher power required?

[Esquilax]

Atheists and Christians lead the same moral lives.

Thank you, some theists don't even get that far.

Most atheists have been Christians before and still live like Christians (as far as moral code goes).

Like Littleendian, I've never lived like a christian. I've been in a church literally once in my life.

Not to mention that the morals of Christianity are the societal norm.

Not really; we don't live in a theocracy run by christianity (not literally, anyway) meaning we're breaking the first commandment right off the bat. Nor do we murder those of different religions... truth is, though we share some highly practical and obvious moral principles with christianity, there are many more that we don't, and moreover those moral principles we "get" from christianity pop up in moral codes that predate christianity too, the code of Hammurabi being the most popular example. Oh, and non-christian societies also share these codes too, generally.

What's more likely is that christianity co-opts the good bits from other moral systems, just like all other religions and moral codes, and that all of this traces back to a somewhat objective moral sense that we as a species have developed over time, simply based on the physical reality in which we live, and the empathic process instilled in us via evolution.

My opinion is that theism traces all of our morals back to God, while (debatably) in atheism, these morals cannot be traced back.

It's amazing how many of my google hits feature evolution since I started posting here.

Actually, we can trace back morality to beyond theism.