Male humpback whales in a population share an evolving song, and novel song types can spread between populations through social learning rather than genes.
Only male humpbacks sing, mostly in the breeding season: a long, repeated sequence of moans, cries and pulses, built from phrases and themes. All the males in one area sing nearly the same song, and it keeps changing as singers add small variations that the others copy. Sometimes the change is sudden. In 1996, researchers off eastern Australia recorded two males singing a song that belonged to the population off western Australia; within two years every singer they recorded had switched to it. Their report in Nature in 2000 called it a cultural revolution, because such a rapid, complete change can only spread by learning. Later studies traced new songs moving eastward, population by population, across the South Pacific.






