The Masses

What is the most important thing in natrual selection/evolution? This is a trick question since most will say how well suited a species is to its environment. The reality is that it is populations size, or in other words how widespread a given mutation becomes. Even the best suited species cannot compete against large numbers of average suited species.
SO...in human existance what is the most important trait; the ability to critically reason or the ability to blindly follow. I will acknowledge that for this discussion I assume that these are genetic characteristics even though this is not fundamental to the argument. It would be assumed that a human that can critically observe its surroundings and make learned decisions would be the most successful...yes, if it was a one on one struggle with a human that had a lesser ability to do this (also assuming this does not include mortal combat). However, people who are more easy to manipulate (whether genetic or human produced), act in large masses and are quick to act compared to the reasoned individual. Does this then mean that in human society, the lockstep mass movements of those that are lesser critical thinkers will triumph over the rag tag poderers?