The literature of ancient Greece and Rome has survived for thousands of years. As a result, Classical literary and philosophical works have served as a profound influence on the writings of subsequent time periods. Indeed, in many subsequent time periods, the ability to quote from Classical sources became a marker of status and intelligence. However, many works of ancient Greece and Rome are not wholly original, but in fact flaunt their use of source materials, citing earlier versions of myths and epics. Often, Classical and post-Classical authors would modify their source materials, and we are able to see them not only as writers, but as readers in their own right.