As early as the second century A. D. , occupations were understood to have ideologies, customs, language, and behaviors that were characteristically their own. Philostratus wrote a handbook for ancient Greek athletic coaches, describing in detail how they differed from teachers of gymnastics. Harrison Trice contends that, within the culture of an organization, contemporary occupations must be recognized as distinct subcultures. Occupations are also dynamic, so that what a watchmaker or miner or computer coder needs to know changes dramatically over time. Recognition of occupations as dynamic subcultures argues for a new emphasis in the study of organizational cultures. The focus must shift from a single, overall organizational culture to the interrelationships and adaptations of many subcultures to each other and to managerial subcultures.