From Sex at Dawn:
It is a common mistake to assume that evolution is a process of improvement, that evolving organisms are progressing toward some final, perfected state. But they, and we, are not. An evolving society or organism simply adapts over the generations to changing conditions. While these modifications may be immediately beneficial, they are not really improvements because external conditions never stop shifting.
This error underlies the assumption that here and now is obviously better than there and then.
Hmm. I think I made this common mistake.