Select groups and organizations embrace practices that perpetuate their inferiority. The result is the phenomenon we call "mediocrity." This article examines the conditions under which mediocrity is selected and maintained by groups over time. Mediocrity is maintained by a key social process: the marginalization of the adept, which is a response to the group problem of what to do with the highly able. The problem arises when a majority of a group is comprised of average members who must decide what to do with high performers in the group. To solve this problem, reward systems are subverted to benefit the less able and the adept are cast as deviant. Marginalization is a resolution of two tensions: marginalization of the adept for their behavior, and protection from the adept for the mediocre. The American research university is used as an example to describe the phenomenon and to formulate a theoretic argument. The forms and consequences of marginalization are discussed. Marginalizing the adept illustrates an anti-meritocratic behavioral pattern which serves to sustain social systems on which all people, however able, depend.