The natural evolution
of all aspects of a given culture
through various sets of moral
and intellectual values
The speed at which this force moves would at first appear to be regulated by how much freedom individuals in a given society feel they have to experiment with all the various forms of physical and emotional expression.
In a society like Japan, (circ 1990's), where radical shifts in individual expression are punished, (incidents of schoolyard teasing and child suicides relating to this have been reported as extremely high in the Japanese educational system), one might think that cultural evolution would advance at a crawl.
However, in comparison to other cultures where the youth, intelligentsia and individuals involved in the various arts are supported and promoted, cultural change does not seem to advance any more quickly.
It appears that Cultural Drift is a force which is much more complex, advancing to a larger and more mysterious rhythm.