I think your premise is flawed. As I understand the bee sting theory, it is not that self-improvement and community-improvement are halted by the effect, just that they are slowed.

Reversing your premise, if you were to take a population of ancestral humans and greatly reduce the stressors on the population (illness, malnutrition, war, etc.) then would you not expect that they would tend to improve their lives at a much faster rate then their contemporaries?

Ancient progress was agonizingly slow by modern standards. Perhaps the bee sting effect is part of the reason why.