According to the Economist's Cultural evolution, a lot of culture is random:

Dr Bentley is finding that random copying seems to drive many forms of cultural change, from patterns on ancient clay pots to preferences for breeds of dog.

For some, this is disappointing. Many students of cultural evolution hope to find analogies with biological evolution by natural selection, not just random drift, when they look at cultural change. Hence the appropriation from biology of the term "mutation rate". There is even a word for what they hope will turn out to be the cultural equivalent of a gene. This word is "meme".

Another blow for cultural critics.