Natalie Angier, writing for the New York Times:
The new work vividly demonstrates that, Putumayo records notwithstanding, humans hold no patent on multiculturalism. As a growing body of research indicates, many social animals learn from one another and cultivate regional variants in skills, conventions and fashions. Some chimpanzees crack open their nuts with a stone hammer on a stone anvil; others prefer wood hammers on wood anvils. The chimpanzees of the Tai forest rain-dance; those of the Gombe tickle themselves. Dr. Jane Goodall reported a fad in one chimpanzee group: a young female started wiggling her hands, and before long, every teen chimp was doing likewise.
Great piece overall, but I found this particular learned dynamic most fascinating!