Being aware that cultures change over time.
Cultures which survive have the property of change. Although some can only be preserved in toto within the environment in which they arose, most can take bits and pieces from other cultures and still retain their identity.
This ability to change must always be kept in the forefront when doing anthropological research. When the research was done has to be part of the analysis, as many cultures undergo changes within a generation or two.
For example, stepping into a lecture theatre in 1970 one would encounter highly politicised students, many actively engaged in the Anti-War Movement, Feminism, Black Power, Civil Rights, etc.
Stepping into the same classroom in 2005 one encounters a rather apathetic bunch, more akin to those of the 1950s, who attended college to gain the qualifications for particular positions (or marry well).
To attempt to use a monograph about University Students written in 1970 to understand the 2005 student, would ensure failure.
Hence, use that image when reading an ethnography done twenty or more years ago. The moment in time an ethnography reflects might be obsolete. One could be studying a culture that no longer exists, making the most horrendous errors in direct encounter.
Although many instructors cling to the studies they read as undergraduates, outside of a critical analysis of the methodology, the document might be worthless. Language changes. Words take up different meanings over time.
In Jamaica in the 1980s, the City buses were called “Chi- Chi” buses, because of the sound they made when stopping. The term “chi-chi”, in the late 90s, became a euphemism for homosexuality.
A new editor, having spent the past fifteen years in London wrote “Chi-Chi bus drivers strike,” which caused a near riot among drivers, and resulted in the Editor having to be removed.
Yes, he was born in Jamaica, attended High School, left for University. The changes in Jamaican Culture in fifteen years made the Peace Corp Worker with six months under her belt, far more fey in the current ‘runnings’ then he was.
Consider everything you “know” of another culture with extreme suspicion. Be very careful in making assumptions. You can glance at a previous ethnography, but don’t use it as a foundation.
Never forget, to survive change is vital, hence the culture you are about to study has changed since that document was published.