Bootstrapped morality

Theists often use the argument that without some kind of super-being (invariably their own particular Deity) there could not be Human morality and we'd all be running around raping and murdering each other; after all, if there's no God then where do we get our sense of right and wrong from?

For atheists this question seems to have a simple and frankly obvious answer, i.e. we get it from ourselves, the thinking goes something like this.

Evolution equipped us (over time) with a basic set of "rules of thumb" that enabled the successful survival of tribes of social primates, if we hadn't thrived then we simply wouldn't now be discussing it. Over time and in recent history our development of "cultures" has sculpted all of the various refinements, deletions and additions to this basic set, particularly the religious dimension of culture. So, we would contend that although religion has certainly refined and influenced our morality over the years, it did not originate it. The reason I conclude this is simply an examination of the evidence, i.e. look around, the world is exactly as you would expect if this hypothesis were true and exactly NOT how your would expect if there were a single Deity dictating objective morality from on-high. There are some simple, self-evident facts that support this idea, for example over time our view of morality changes, we no longer think it's OK to keep slaves whereas years ago we did. Different cultures develop subtly different ideas of what is moral, usually conforming to parochial power struggles and practical geographical needs. Human beings develop very similar ideas about morality even when they are isolated from each other, many indigenous peoples in remote parts of the world have very similar ideas to Christians, Jews and Muslims about things like stealing; despite knowing nothing of the existence of those religions.

This is not a new argument or a new viewpoint of course, many philosophers and theologians have debated the ins and outs of where morality comes from for millennia, but for a lot of people the concept of subjective morality seems to be an intellectual road-block, they just can't grasp it without the idea of a celestial dictatorship entering into the frame somehow. I came across the following photograph the other day which made me think about how the concept might be explained to such people, I think it fits the atheist viewpoint (and our experience of reality) particularly well.