Can't believe I missed this thread, I love these sorts of questions.
Now, to memory, all these people didn't believe in an afterlife or a soul. Essentially completely in disbelief of the supernatural. So if I put myself in the shoes of someone with those belief's I come up with this scenario: If there is no God, no Hell, and no Heaven, or even any form of life after I die, what is the point of having any form of moral compass? I can do whatever I want as long as it benefits me more then it harms me throughout my life, since after I die I won't have to worry about anything.
Technically speaking, you're not wrong. However, although I can tell you're trying to understand the atheist mindset, you're running into trouble because your latent (presumably Christian) approach to the matter is backwards of ours.
The way I see it, the question you're asking boils down to something very similar to the popular Christian question, "how could everything have fallen perfectly into place to form this beautiful world by chance?"
Technically speaking, the earth and everything on it did fall into place by chance, but that's a backwards way of looking at it. It would be more accurate to say, "If everything didn't fall into place that way, the earth wouldn't exist as it does--it would simply be different." The reason this concept is hard for Christians to grasp is because they're hardwired to see life and such as what everything happened to produce rather than what was produced by everything that happened.
Our difference in perspective is similar in regards to morality, if that makes sense. From an atheistic perspective, morality forms around a common interest in cohesive society. From a Christian perspective, cohesive society forms around a common sense of morality.
There is also the fact that with these same belief that there is no afterlife, suicide is an extremely appealing option for people of high stress levels and depression.
It sure is. That's probably the reason they made sure to threaten eternal torture for doing it in the Bible.
I simply do not understand where a moral compass is if an individual does not believe in an afterlife of one form or another. So for any in that situation please enlighten me to your reasoning. And even if you aren't in that same situation, if you think you figured out their reasoning, please tell me anyway. Could be useful for an extra view.
Here's your answer: It's no different than where yours comes from. You claim your sense of morality is largely based on how you will be rewarded or punished when you die; in other words, doesn't it all come back to self-interest whether you believe in an afterlife or not?