This my Answer to the stackoverflow question: History of changes to a particular line of code in Subversion?:
A start is the command svn blame (or annotate,praise). It will show you when a line of code was last modified and by whom it was modified. e.g.:
4564 wiemann # $Id$
4564 wiemann # Author: David Goodger <goodger@python.org>
778 goodger # Copyright: This module has been placed in the public domain.
217 goodger