Negative selection (politics)

Negative selection is a political process that occurs especially in rigid hierarchies, most notably dictatorships, but also to lesser degrees in such settings as corporations or electoral politics.
The person on the top of the hierarchy, wishing to remain in power forever, chooses his associates with the prime criterion of incompetence – they must not be competent enough to remove him from power. Since subordinates often mimic their leader, these associates do the same with those below them in the hierarchy, and the hierarchy becomes progressively filled over time with more and more incompetent people.
If the dictator sees that he is threatened nonetheless, he will remove those that threaten him from their positions – "purge" the hierarchy. Emptied positions in the hierarchy are normally filled with people from below – those who were less competent than their previous leaders. So, over the course of time, the hierarchy turns less and less effective. Once the dictator dies – or is removed by some external force – what remains is a grossly ineffective hierarchy.
In a famous anecdote from Herodotus's "Histories", a messenger from Periander asks Thrasybulus for advice on ruling. Thrasybulus, instead of responding, takes the messenger for a walk in a field of wheat, where he proceeds to cut off all of the best and tallest ears of wheat. The message, correctly interpreted by Periander, was that a wise ruler would preempt challenges to his rule by "removing" those prominent men who might be powerful enough to challenge him.