Most of their native practices like speaking their shitty language, eating each other, and "dancing" obnoxiously had laregly died out by the 50s and 60s. Commies convinced them to get back to their roots at the same time the american plains niggers were blowing shit up. So the youth had to learn the haka from from their grandparents and great grandparents who were cannibals. Cannibals often get prion diseases. One of the symptoms is trembling and muscle twitches. Seems like it could be possible half the shit we see in a haka is just a result diseased old cannibals not being able to control their muscles anymore.