Chimpanzee culture on Material World

There was a great piece on this afternoon's Material World - an interview with Andrew Whiten about cultural traditions in chimpanzees. Andrew Whiten makes the very interesting observation that while many animals appear to have 'traditions' (i.e. separate groups of the same bird species with different birdsong), chimpanzee have dozens of traditions. Does this mean that chimps have culture? I think so, yes.

Chimp culture appears, however, to have remained relatively static - Whiten observes that archeological investigation has shown traditions to have persisted for hundreds if not thousands of years. Longer, I would suspect, given that anatomically modern chimps have been around for over six million years. In other words, the big bang of human cultural evolution has never happened for chimps. What cognitive deficit in chimps might account for this..?