I think that the concept of an afterlife would have some type of impact on human behavior.  If an individual is concerned of their own condition in the afterlife, it might play a large role in how they behave in this life.  For example, if someone is concerned with redemption in the afterlife being dependent on how they act in this one, their actions might be in line with what the expectation for behavior should be.  Yet, by the same token, if individuals were not concerned with the presence of the afterlife or some type of judgment outside of it, they might not find a need to moderate their actions.  In the end, the impact of the afterlife on human behavior is dependent on how strongly individuals accept its premise. It is also dependent on how much individuals wish to embrace its influence on this life.  It in this capacity where the role and function of the afterlife holds an impact on whether or not one acts accordingly.  This makes the prospect of an afterlife something that is nearly impossible to determine without understanding where an individual stands on the issue of the afterlife.