To be fair, if you believe in evolution, thinking of things in terms of improvement is very subjective. Evolution isn't selecting for improvement, it's selecting for survival, which may or may not be correlated with your vision of improvement. Think of cockroaches.

From a christian perspective, the natural discontent stems from the fallen nature of man. You're worldly accomplishments will never be able to satisfy that discontentment, as the two areas are unrelated.